Plant hormones (Literature sources on phytohormones and plant signalling)

Journal of Experimental Botany (2023)

Abstract: "Despite its prominent role as a stress hormone and its related importance for agriculture, abscisic acid (ABA) molecular signaling is poorly characterized in crops such as potato (Solanum tuberosum). Potato is the world’s third most produced food crop and the most prominent non-cereal in terms of production and consumption (FAOSTAT, 2021). Its importance as a staple food is increasing worldwide. With the immediate need for stress-tolerant and more resilient plants due to changing climate patterns, research on ABA functions in potato will be essential to maintain productivity. Moreover, multiple developmental and physiological aspects of ABA unrelated to abiotic stresses are often overlooked and are difficult to study in plant models. Investigating putative ABA signaling players in potato plants, Liu et al. (2023) have deciphered the negative role of the phosphatase StHAB1 on ABA perception and potato drought stress responses. In addition, the authors provide conclusive evidence that ABA signaling is required for maintaining dormancy in aerial lateral buds. It has long been known that ABA stimulates tuber formation, but the molecular details of such mechanisms remain unknown. It was recently shown that the development of aerial lateral buds leads to a reduction in underground tuber production (Nicolas et al., 2022). Therefore, the ABA-mediated blockage of lateral bud outgrowth reported by Liu et al. (2023) may provide a molecular explanation of the effects of ABA on tuber formation. The transgenic potato lines created in this study offer excellent genetic tools for further study of these connections and have potential biotechnological implications. This work underscores the importance of translational research from models to crops and how it is key not to circumscribe observations to obvious outputs in functional analysis in non-model plants."

Journal of Plant Growth Regulation (2021)

Abstract: "Over the last years, cytokinin deficiency has been studied in a variety of plant species, using transgenic expression of cytokinin oxidase/dehydrogenase genes (CKX). In tobacco and Arabidopsis thaliana, overexpression of A. thaliana CKX genes caused changes in plant morphology known as the "cytokinin deficiency syndrome", including stunted shoot growth, decreased apical dominance, and enhanced root growth. For a valid comparison with the previously obtained in vitro grown AtCKX2-transgenic potato lines, we report here on the construction of transgenic lines of the cultivar Désirée constitutively expressing the gene AtCKX1 under control of the CaMV 35S promoter. Three lines expressing the transgene in both shoot and root tissues were used for analysis. Analyses of CKX activity of tissue extracts, cytokinin levels, morphology, and tuberization parameters revealed similarities as well as differences from the AtCKX2-transgenic plants, including lower levels of CKX activity, and more pronounced morphological effects of cytokinin deficiency. One of the three AtCKX1-overexpressing potato lines was able to start forming tubers before 30 days of growth in long day conditions (16 h/8 h photoperiod) as has been previously observed in some AtCKX2 overexpressors. The extension of the experimental period to 120 days of growth in vitro showed that the other two AtCKX1-overexpressing lines showed impaired tuberization in terms of the number of tubers per plant, and tuber size. We conclude that cytokinin deficiency has distinct effects on tuber induction and tuber initiation/growth, possibly mediated by distinct signaling mechanisms."