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Authors: Jianhong Hu, Xiao Li and Tai-ping Sun.
Nature Plants (2023)
Editor's view: Mutant combinations of four AUXIN RESPONSE FACTORs in tomato by CRISPR–Cas9 technology reveal their dual function in inhibiting fruit set before pollination while activating fruit growth after fertilization.
Abstract: "In flowering plants, auxin produced in seeds after fertilization promotes fruit initiation. The application of auxin to unpollinated ovaries can also induce parthenocarpy (seedless fruit production). Previous studies have shown that auxin signalling components SlIAA9 and SlARF7 (a class A AUXIN RESPONSE FACTOR (ARF)) are key repressors of fruit initiation in tomato (Solanum lycopersicum). A similar repressive role of class A ARFs in fruit set has also been observed in other plant species. However, evidence is lacking for a role of any class A ARF in promoting fruit development as predicted in the current auxin signalling model. Here we generated higher-order tomato mutants of four class A SlARFs (SlARF5, SlARF7, SlARF8A and SlARF8B) and uncovered their precise combinatorial roles that lead to suppressing and promoting fruit development. All four class A SlARFs together with SlIAA9 inhibited fruit initiation but promoted subsequent fruit growth. Transgenic tomato lines expressing truncated SlARF8A/8B lacking the IAA9-interacting PB1 domain displayed strong parthenocarpy, further confirming the promoting role of SlARF8A/8B in fruit growth. Altering the doses of these four SlARFs led to biphasic fruit growth responses, showing their versatile dual roles as both negative and positive regulators. RNA-seq and chromatin immunoprecipitation–quantitative PCR analyses further identified SlARF8A/8B target genes, including those encoding MADS-BOX transcription factors (AG1, MADS2 and AGL6) that are key repressors of fruit set. These results support the idea that SlIAA9/SlARFs directly regulate the transcription of these MADS-BOX genes to inhibit fruit set. Our study reveals the previously unknown dual function of four class A SlARFs in tomato fruit development and illuminates the complex combinatorial effects of multiple ARFs in controlling auxin-mediated fruit set and fruit growth."
Authors: Yue Liu, Yang Li, Huixin Guo, Bingsheng Lv, Jing Feng, Huihui Wang, Zhonghua Zhang and Sen Chai.
Horticulture Research (2023)
Abstract: "Spraying N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU), an exogenous cytokinin (CK) growth regulator, is the conventional method for inducing fruit set during melon (Cucumis melo L.) production; however, the mechanism by which CPPU induces fruit set is unclear. Through histological and morphological observations, the fruit size was comparable between CPPU-induced fruits and normal pollinated fruits because CPPU-induced fruits had higher cell density but smaller cell size compared to normal pollinated fruits. CPPU promotes the accumulation of gibberellin (GA) and auxin and decreases the level of abscisic acid (ABA) during fruit set. Moreover, application of the GA inhibitor paclobutrazol (PAC) partially inhibits CPPU-induced fruit set. Transcriptome analysis revealed that CPPU-induced fruit set specifically induced the GA-related pathway, in which the key synthase encoding gibberellin 20-oxidase 1 (CmGA20ox1) was specifically up-regulated. Further study indicated that the two-component response regulator 2 (CmRR2) of the cytokinin signaling pathway, which is highly expressed at fruit setting, positively regulates the expression of CmGA20ox1. Collectively, our study determined that CPPU-induced melon fruit set is dependent on GA biosynthesis, providing a theoretical basis for the creation of parthenocarpic melon germplasm."
Authors: Shaobo Niu, Yu He, Siwei Yan, Zhengliang Sun, Run Cai and Yan Zhang.
Horticultural Plant Journal (2023)
Abstract: "Gibberellin (GA) is one of the major plant hormones that promote parthenocarpy, a highly valuable agronomic trait. Here, we demonstrated that exogenous GA3 application triggered the formation of parthenocarpic fruits with smaller size but unchanged shape in tomato (Solanum lycopersicum). These fruits exhibited a thicker pericarp, undeveloped ovules, and few jelly tissues, leading to smaller locules with empty cavities. Histological investigation showed that GA treatment produced more cell layers with larger cells in the pericarp, suggesting its promotion in both cell division and expansion. Transcriptomic analyses between GA3- and mock-treated unpollinated ovaries/fruits identified a large number of differentially expressed genes related to hormones, cell division, cell expansion, and transcription factors, implying that they coordinately regulated parthenocarpy conferred by GA. In particular, the downregulation of five reported repressors of tomato parthenocarpy, including two auxin signaling components, AUXIN RESPONSE FACTOR5 (SlARF5) and SlARF7, and three MADS-box genes, TOMATO APETALA3 (TAP3), TOMATO PISTILLATA (TPI), and AGAMOUS-LIKE6 (SlAGL6), after GA treatment might play a key role in this process. Furthermore, we found that the knockdown of a GA signaling factor SlMYB33, which was depressed by GA treatment, induced parthenocarpic fruit set in tomato, an effect that might have been achieved by enhancing GA biosynthesis and decreasing the expression of some repressors of tomato parthenocarpy. Thus, our results provide a basis for understanding the regulatory mechanism of GA in tomato parthenocarpy."
Authors: Edoardo Vignati, Marzena Lipska, Jim M. Dunwell, Mario Caccamo and Andrew J. Simkin.
Planta (2022)
Main conclusion: This manuscript identifies cherry orthologues of genes implicated in the development of pericarpic fruit and pinpoints potential options and restrictions in the use of these targets for commercial exploitation of parthenocarpic cherry fruit.
Abstract: "Cherry fruit contain a large stone and seed, making processing of the fruit laborious and consumption by the consumer challenging, inconvenient to eat ‘on the move’ and potentially dangerous for children. Availability of fruit lacking the stone and seed would be potentially transformative for the cherry industry, since such fruit would be easier to process and would increase consumer demand because of the potential reduction in costs. This review will explore the background of seedless fruit, in the context of the ambition to produce the first seedless cherry, carry out an in-depth analysis of the current literature around parthenocarpy in fruit, and discuss the available technology and potential for producing seedless cherry fruit as an ‘ultimate snacking product’ for the twenty-first century."
Authors: Rahat Sharif, Li Su, Xuehao Chen and Xiaohua Qi.
Horticulture Research (2022)
Abstract: "In some horticultural crops, such as Cucurbitaceae, Solanaceae, and Rosaceae species, fruit set and development can occur without the fertilization of ovules, a process known as parthenocarpy. Parthenocarpy is an important agricultural trait that can not only mitigate fruit yield losses caused by environmental stresses but can also induce the development of seedless fruit, which is a desirable trait for consumers. In the present review, the induction of parthenocarpic fruit by the application of hormones such as auxins (2,4 dichlorophenoxyacetic acid; naphthaleneacetic acid), cytokinins (forchlorfenuron; 6-benzylaminopurine), gibberellic acids, and brassinosteroids is first presented. Then, the molecular mechanisms of parthenocarpic fruit formation, mainly related to plant hormones, are presented. Auxins, gibberellic acids, and cytokinins are categorized as primary players in initiating fruit set. Other hormones, such as ethylene, brassinosteroids, and melatonin, also participate in parthenocarpic fruit formation. Additionally, synergistic and antagonistic crosstalk between these hormones is crucial for deciding the fate of fruit set. Finally, we highlight knowledge gaps and suggest future directions of research on parthenocarpic fruit formation in horticultural crops.
Authors: Eder M. da Silva and Fabio T.S. Nogueira.
Molecular Plant (2021)
Excerpts: "Given that fruit development is controlled by a network of physiological and molecular pathways, parthenocarpy - defined as the fertilization‐ independent seedless fruit set - may be achieved through hormone treatment or by altering specific genetic programs (Silva et al., 2017; Joldersma and Liu, 2017). MicroRNAs (miRNAs) are crucial regulators in several genetic programs and, together with their targets, configurate the so-called miRNA regulatory modules. Several miRNA regulatory modules interplay with hormone networks to regulate plant reproduction, including various stages of fruit development (Correa et al., 2018)."
"In a recent study, Clepet and colleagues (2021) found a new miRNA regulatory module that controls ovule development and fruit setting in tomato (Solanum lycopersicum). They isolated miR166-targeted SlHB15A mutants that exhibit aberrant ovules and parthenocarpic fruits under normal and adverse temperature conditions. MiR166-targeted SlHB15A is expressed in the ovule integument and directly regulates auxin and ethylene signaling to prevent fruit set in the absence of fertilization (Figure 1)."
Authors: Long Thien Tran, Anh Tuan Nguyen, Minh Hong Nguyen, Long Tien Nguyen, Minh Thi Nguyen, Lai Thi Trinh, Dieu-Thuy Thi Tran, Sang Viet Ta, Ken Hoshikawa, Koichi Sugimoto and Hiroshi Ezura.
Euphytica (2021)
Abstract: "A number of different strategies have been utilized to introduce parthenocarpy into tomato commercial cultivars. In this study, we evaluated three segregating populations (F2, F3, and F4) derived from conventional crossing between iaa9-3 mutant in Micro-Tom and an inbred pure tomato line V62. The mutation caused potato leaf style and high parthenocarpic fruit set ratio (nearly 90%). Introducing iaa9-3 mutation into tomato cultivar has some advantages over other parthenocarpic mutants, including, (1) retaining the normal stamen structure and fertile pollen; (2) the parthenocarpic lines can produce sufficient seeds for self-pollinated propagation; (3) average seedless fruit weight of experimental lines ranged from 25 g/fruit (small category) to over 50 g/fruit (intermediate category), together with good number of fruits/plant which can lead to a theoretical seedless fruit yield of over 3000 g/plant, which is acceptable for commercial varieties; (4) increasing the quality of seedless fruits compared to seeded fruits which is attributable to an increase in the mass of placental area and a higher Brix level than locule and pericarp areas. The selected iaa9-3 mutant lines should be used to develop the tomato parthenocarpic varieties with high seedless fruit yields and quality."
Authors: Haiqi Zhang, Wei Han, Huibin Wang, Liu Cong, Rui Zhai, Chengquan Yang, Zhigang Wang and Lingfei Xu.
Research Square (2021)
Abstract: "Background: Parthenocarpy results in traits attractive to both consumers and breeders, and it overcomes the obstacle of self-incompatibility in the fruit set of horticultural crops, including pear (Pyrus bretschneideri). However, there is limited knowledge regarding the genetic and molecular mechanisms that regulate parthenogenesis. Results: Here, in a transcriptional comparison between pollination-dependent and GA4-induced parthenocarpy, PbCYP78A6 was identified and proposed as a candidate gene involved in parthenocarpy. PbCYP78A6 is similar to Arabidopsis thaliana CYP78A6 and is highly expressed in pear hypanthia. The increased PbCYP78A6 expression, as assessed by RT-qPCR, was induced by pollination and GA4 exposure. The ectopic overexpression of PbCYP78A6 contributed to parthenocarpic fruit production in tomato. The PbCYP78A6 expression coincided with fertilized and parthenocarpic fruitlet development and the expression of fruit development-related genes as assessed by cytological observations and RT-qPCR, respectively. PbCYP78A6 RNA interference and overexpression revealed that the gene is an upstream regulator of fruit development-related genes in pear. Conclusions: Our findings indicate that PbCYP78A6 plays a critical role in cell proliferation and provide insights into controlling parthenocarpy."
Authors: Miaoqing Wang, Li Su, Yi Cong, Jingjing Chen, Youling Geng, Chunlu Qian, Qiang Xu, Xuehao Chen and Xiaohua Qi.
Scientia Horticulturae (2021)
Highlights: • Endogenous carbohydrates levels affect the parthenocarpic fruit set of cucumber. • Exogenous sugars induced parthenocarpic fruit initiation. • Sugars enhance parthenocarpic fruit set through auxin and cytokinin signaling.
Abstract: "Parthenocarpy is an important agricultural trait that determines the yield of cucumber. The role of sugars in parthenocarpic fruit formation is unknown. Therefore, we investigated these factors by using one highly parthenocarpic line DDX and one weakly parthenocarpic line ZK. To identify the possible effect of photosynthesis on parthenocarpy, leaf of ZK and DDX were covered for limiting the synthesis of carbohydrates. Leaf covering inhibited parthenocarpic fruit initiation and growth. Sugars (sucrose, fructose and glucose) contents in CPPU-induced, pollinated fruit of ZK and non-pollinated fruit of DDX were higher than those in non-pollinated fruit of ZK. The exogenous application of sugars (especially fructose and sucrose) significantly induced the parthenocarpic fruit set and growth. Transcriptomes of fruits treated with and without exogenously applied sugars showed that genes involved in auxin signaling and cytokinin signaling were more strongly expressed in the treated fruits. Auxin responsive gene IAA14, and cytokinin responsive genes encoding histidine-containing phosphotransfer protein 4 and two-component response regulator 17 were upregulated in sugar-induced parthenocarpic fruits. These results show that parthenocarpic fruit formation is regulated by the interplay among sugars and the plant hormones auxin and cytokinin."
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Authors: Rui Lu, Mengting Pi, Zhongchi Liu and Chunying Kang.
The Plant Journal (2023)
Abstract: "Auxin plays an essential role in plant growth and development, particularly in fruit development. The YUCCA (YUC) genes encode flavin monooxygenases that catalyze a rate-limiting step in auxin biosynthesis. Mutations that disrupt YUC gene function provide useful tools for dissecting general and specific functions of auxin during plant development. In woodland strawberry (Fragaria vesca), two EMS mutants, Y422 and Y1011, have been identified that exhibit severe defects in leaves and flowers. In particular, the width of the leaf blade is greatly reduced and each leaflet in the mutants has fewer and deeper serrations. In addition, the number and shape of the floral organs are altered, resulting in smaller fruits. Mapping by sequencing revealed that both mutations reside in the FveYUC4 gene and were therefore renamed as yuc4-1 and yuc4-2. Consistent with a role for FveYUC4 in auxin synthesis, free auxin and its metabolites are significantly reduced in the yuc4 leaves and flowers. This role of FveYUC4 in leaf and flower development is supported by its high and specific expression in young leaves and flower buds using GUS reporters. Furthermore, germline transformation of pYUC4::YUC4, which resulted in elevated expression of FveYUC4 in yuc4 mutants, not only rescued the leaf and flower defects but also produced parthenocarpic fruits. Taken together, our data demonstrate that FveYUC4 is essential for leaf and flower morphogenesis in woodland strawberry by providing auxin hormone at the proper time and in the right tissues."
Authors: Alon Israeli, Ramona Schubert, Nave Man, Naama Teboul, Juan Carlos Serrani Yarce, Emily E. Rosowski, Miin-Feng Wu, Matan Levy, Idan Efroni, Karin Ljung, Bettina Hause, Jason W. Reed and Naomi Ori.
Plant Physiology (2023)
Abstract: "Fruit formation depends on successful fertilization and is highly sensitive to weather fluctuations that affect pollination. Auxin promotes fruit initiation and growth following fertilization. Class A auxin response factors (Class A ARFs) repress transcription in the absence of auxin and activate transcription in its presence. Here we explore how multiple members of the ARF family regulate fruit set and fruit growth in tomato (Solanum lycopersicum) and Arabidopsis thaliana, and test whether reduction of SlARF activity improves yield stability in fluctuating temperatures. We found that several tomato Slarf mutant combinations produced seedless parthenocarpic fruits, most notably mutants deficient in SlARF8A and SlARF8B genes. Arabidopsis Atarf8 mutants deficient in the orthologous gene had less complete parthenocarpy than did tomato Slarf8a Slarf8b mutants. Conversely, Atarf6 Atarf8 double mutants had reduced fruit growth after fertilization. AtARF6 and AtARF8 likely switch from repression to activation of fruit growth in response to a fertilization-induced auxin increase in gynoecia. Tomato plants with reduced SlARF8A and SlARF8B gene dosage had substantially higher yield than the wild type under controlled or ambient hot and cold growth conditions. In field trials, partial reduction in the SlARF8 dose increased yield under extreme temperature with minimal pleiotropic effects. The stable yield of the mutant plants resulted from a combination of early onset of fruit set, more fruit-bearing branches and more flowers setting fruits. Thus, ARF8 proteins mediate the control of fruit set, and relieving this control with Slarf8 mutations may be utilized in breeding to increase yield stability in tomato and other crops."
Authors: Xiaojia Zhang, Baolin Zhao, Yibo Sun and Yulong Feng.
Frontiers in Plant Science (2022)
Abstract: "Horticultural plants such as vegetables, fruits, and ornamental plants are crucial to human life and socioeconomic development. Gibberellins (GAs), a class of diterpenoid compounds, control numerous developmental processes of plants. The roles of GAs in regulating growth and development of horticultural plants, and in regulating significant progress have been clarified. These findings have significant implications for promoting the quality and quantity of the products of horticultural plants. Here we review recent progress in determining the roles of GAs (including biosynthesis and signaling) in regulating plant stature, axillary meristem outgrowth, compound leaf development, flowering time, and parthenocarpy. These findings will provide a solid foundation for further improving the quality and quantity of horticultural plants products."
Authors: Miyako Kusano, Kanjana Worarad, Atsushi Fukushima,Ken Kamiya, Yuka Mitani, Yozo Okazaki, Yasuhiro Higashi, Ryo Nakabayashi, Makoto Kobayashi, Tetsuya Mori, Tomoko Nishizawa, Yumiko Takebayashi, Mikiko Kojima, Hitoshi Sakakibara, Kazuki Saito, Shuhei Hao, Yoshihito Shinozaki, Yoshihiro Okabe, Junji Kimbara,Tohru Ariizumi and Hiroshi Ezura.
Cells (2022)
Abstract: "Parthenocarpy, the pollination-independent fruit set, can raise the productivity of the fruit set even under adverse factors during the reproductive phase. The application of plant hormones stimulates parthenocarpy, but artificial hormones incur extra financial and labour costs to farmers and can induce the formation of deformed fruit. This study examines the performance of parthenocarpic mutants having no transcription factors of SlIAA9 and SlTAP3 and sldella that do not have the protein-coding gene, SlDELLA, in tomato (cv. Micro-Tom). At 0 day after the flowering (DAF) stage and DAFs after pollination, the sliaa9 mutant demonstrated increased pistil development compared to the other two mutants and wild type (WT). In contrast to WT and the other mutants, the sliaa9 mutant with pollination efficiently stimulated the build-up of auxin and GAs after flowering. Alterations in both transcript and metabolite profiles existed for WT with and without pollination, while the three mutants without pollination demonstrated the comparable metabolomic status of pollinated WT. Network analysis showed key modules linked to photosynthesis, sugar metabolism and cell proliferation. Equivalent modules were noticed in the famous parthenocarpic cultivars ‘Severianin’, particularly for emasculated samples. Our discovery indicates that controlling the genes and metabolites proffers future breeding policies for tomatoes.
Authors: Suthanthiram Backiyarani, Rajendran Sasikala, Simeon Sharmiladevi and Subbaraya Uma.
Scientific Reports (2021)
Abstract: "Banana, one of the most important staple fruit among global consumers is highly sterile owing to natural parthenocarpy. Identification of genetic factors responsible for parthenocarpy would facilitate the conventional breeders to improve the seeded accessions. We have constructed Protein–protein interaction (PPI) network through mining differentially expressed genes and the genes used for transgenic studies with respect to parthenocarpy. Based on the topological and pathway enrichment analysis of proteins in PPI network, 12 candidate genes were shortlisted. By further validating these candidate genes in seeded and seedless accession of Musa spp. we put forward MaAGL8, MaMADS16, MaGH3.8, MaMADS29, MaRGA1, MaEXPA1, MaGID1C, MaHK2 and MaBAM1 as possible target genes in the study of natural parthenocarpy. In contrary, expression profile of MaACLB-2 and MaZEP is anticipated to highlight the difference in artificially induced and natural parthenocarpy. By exploring the PPI of validated genes from the network, we postulated a putative pathway that bring insights into the significance of cytokinin mediated CLAVATA(CLV)–WUSHEL(WUS) signaling pathway in addition to gibberellin mediated auxin signaling in parthenocarpy. Our analysis is the first attempt to identify candidate genes and to hypothesize a putative mechanism that bridges the gaps in understanding natural parthenocarpy through PPI network."
Authors: Haiqi Zhang, Wei Han, Huibin Wang, Liu Cong, Rui Zhai, Chengquan Yang, Zhigang Wang and Lingfei Xu.
BMC Plant Biology (2021)
Abstract: "Background - Parthenocarpy results in traits attractive to both consumers and breeders, and it overcomes the obstacle of self-incompatibility in the fruit set of horticultural crops, including pear (Pyrus bretshneider). However, there is limited knowledge regarding the genetic and molecular mechanisms that regulate parthenogenesis. Results - Here, in a transcriptional comparison between pollination-dependent fruit and GA4-induced parthenocarpy, PbCYP78A6 was identified and proposed as a candidate gene involved in parthenocarpy. PbCYP78A6 is similar to Arabidopsis thaliana CYP78A6 and highly expressed in pear hypanthia. The increased PbCYP78A6 expression, as assessed by RT-qPCR, was induced by pollination and GA4 exposure. The ectopic overexpression of PbCYP78A6 contributed to parthenocarpic fruit production in tomato. The PbCYP78A6 expression coincided with fertilized and parthenocarpic fruitlets development and the expression of fruit development-related genes as assessed by cytological observations and RT-qPCR, respectively. PbCYP78A6 RNA interference and overexpression in pear calli revealed that the gene is an upstream regulator of specific fruit development-related genes in pear. Conclusions - Our findings indicate that PbCYP78A6 plays a critical role in fruit formation and provide insights into controlling parthenocarpy."
Authors: Christian Clepet, Ravi Sureshbhai Devani, Rachid Boumlik, Yanwei Hao, Halima Morin, Fabien Marcel, Marion Verdenaud, Brahim Mania, Gwilherm Brisou, Sylvie Citerne, Gregory Mouille, Jean-Christophe Lepeltier, Shai Koussevitzky, Adnane Boualem and Abdelhafid Bendahmane.
Molecular Plant (2021)
Abstract: "Fruit set is inhibited by adverse temperatures, with consequences on yield. We isolated a tomato mutant producing fruits under non-permissive hot temperatures and identified the causal gene as SlHB15A, belonging to class-III homeodomain leucine-zipper transcription factors (HD-ZipIII). SlHB15A loss-of-function mutants display aberrant ovule development that mimics transcriptional changes occurring in fertilized ovules and leads to parthenocarpic fruit set under optimal and non-permissive temperatures, in field and glasshouse conditions. Under cold growing condition, SlHB15A is subjected to conditional haploinsufficiency and recessive dosage sensitivity controlled by microRNA 166 (miR166). Knockdown of SlHB15A alleles by miR166 leads to a continuum of aberrant ovules correlating with parthenocarpic fruit set. Consistent with this, plants harboring SlHB15A-miRNA166 resistant allele developed normal ovules and were unable to set parthenocarpic fruit under cold condition. DNA affinity purification sequencing (DAP-seq) and RNAseq analyses revealed SlHB15A is a bifunctional transcription factor, expressing in the ovule integument. SlHB15A binds to the promoters of auxin genes to repress auxin signaling and to ethylene genes to activate their expression. Survey of tomato genetic biodiversity identified pat and pat-1, two historical parthenocarpic mutants, as alleles of SlHB15A. Our finding demonstrates the role of SlHB15A as a sentinel to prevent fruit set in the absence of fertilization and provides a mean to enhance fruiting under extreme temperatures."
Authors: Backiyarani Suthanthiram, Sasikala Rajendran, Sharmiladevi Simeon and Uma Subbaraya.
Research Square (2021)
Abstract: "Banana, one of the most important staple, delicious fruit among global consumers is highly sterile owing to natural parthenocarpy. Identification of genetic factors responsible for parthenocarpy would facilitate the conventional breeders to improve the seeded accessions. We have constructed Protein-protein interaction (PPI) network through mining differentially expressed genes and the genes used for transgenic studies with respect to parthenocarpy. Based on the topological and pathway enrichment analysis of proteins in PPI network, 12 candidate genes were shortlisted. By exploring the PPI of candidate genes from the putative network, we postulated a putative pathway that bring insights into the significance of cytokinin mediated CLV-WUSHEL signaling pathway in addition to gibberellin mediated auxin signaling pathway in parthenocarpy. Further validation of candidate genes in seeded and seedless accession of Musa spp using qRT-PCR put forward AGL8, MADS16, IAA (GH3.8), RGA1, EXPA1, GID1C, HK2 and BAM1 as possible target genes in natural parthenocarpy. In contrary, expression profile of ACLB-2 and ZEP is anticipated to highlight the difference in artificially induced and natural parthenocarpy. Our analysis is the first attempt to identify candidate genes and to hypothesize a putative mechanism that bridges the gaps in understanding natural parthenocarpy through protein-protein interaction network."
Authors: Li Su, Sharif Rahat, Nannan Ren, Mikiko Kojima, Yumiko Takebayashi, Hitoshi Sakakibara, Miaoqing Wang, Xuehao Chen and Xiaohua Qi.
Scientia Horticulturae (2021)
Highlights: • Cytokinin and gibberellic acid concentrations were positive correlated with parthenocarpy in cucumber. • Cytokinin, auxin and GA4 + 7 could induce the parthenocarpic fruit set in cucumber. • Cytokinin- and auxin-related genes contribute to high parthenocarpic fruit formation in cucumber.
Abstract: "Parthenocarpy (fruit development without pollination) is an important agricultural trait, which determines the production of horticultural crops like tomato, eggplant and cucumber. Parthenocarpy ability varies widely among cucumber lines. To better understand the genetic regulators underlying this variation, hormone and transcriptome profiles and the expressions of hormone-related genes in non-pollinated fruit of a highly parthenocarpic line DDX and a weakly parthenocarpic line ZK were compared at 1 day after anthesis. The cytokinin and gibberellic acid contents were higher in DDX than in ZK, while the abscisic acid content was less. Exogenous application of cytokinins, auxin and gibberellic acid 4 + 7 successfully induced the parthenocarpic fruit set of ZK. The transcript levels of several cytokinin biosynthesis genes (CsCYP735A1, CsCYP735A2 and CsLOG1), cytokinin-responsive genes (CsRR8/9b, CsRR8/9d, CsRR8/9e and CsRR16/17) and auxin signal transduction genes (Aux/IAAs) were greater in DDX than in ZK, while the level of an abscisic acid receptor (CsPYR1) was lower. These results suggest that high expression levels of cytokinin- and auxin-related genes in DDX contribute to its high parthenocarpy ability."
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