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Authors: Mizuki Murao, Rika Kato, Shuhei Kusano, Rina Hisamatsu, Hitoshi Endo, Yasuki Kawabata, Seisuke Kimura, Ayato Sato, Hitoshi Mori, Kenichiro Itami, Keiko U. Torii, Shinya Hagihara and Naoyuki Uchida.
Plant and Cell Physiology (2023)
Abstract: "Plant seedlings adjust the growth of the hypocotyl in response to surrounding environmental changes. Genetic studies have revealed key players and pathways in hypocotyl growth, such as phytohormones and light signaling. However, because of genetic redundancy in the genome, it is expected that not-yet-revealed mechanisms can be elucidated through approaches different from genetic ones. Here we identified a small compound, HYGIC (HG), that simultaneously induces hypocotyl elongation and thickening, accompanied by increased nuclear size and enlargement of cortex cells. HG-induced hypocotyl growth required the ethylene signaling pathway activated by endogenous ethylene, involving CONSTITUTIVE PHOTOMORPHOGENIC 1, ETHYLENE INSENSITIVE 2, and redundant transcription factors for ethylene responses, ETHYLENE INSENSITIVE 3 (EIN3) and EIN3 LIKE 1. By using EBS:GUS, a transcriptional reporter of ethylene responses based on an EIN3-binding-cis-element, we found that HG treatment ectopically activates ethylene responses at the epidermis and cortex of the hypocotyl. RNA-seq and subsequent gene ontology analysis revealed that a significant number of HG-induced genes are related to responses to hypoxia. Indeed, submergence, a representative environment where the hypoxia response is induced in nature, promoted ethylene-signaling-dependent hypocotyl elongation and thickening accompanied by ethylene responses at the epidermis and cortex, which resembled the HG treatment. Collectively, the identification and analysis of HG revealed that ectopic responsiveness to ethylene promotes hypocotyl growth, and this mechanism is activated under submergence."
Authors: Ravi Ramesh Pathak, Vikas Kumar Mandal, Annie Prasanna Jangam, Narendra Sharma, Bhumika Madan, Dinesh Kumar Jaiswal and Nandula Raghuram.
Scientific Reports (2021)
Abstract: "G-proteins are implicated in plant productivity, but their genome-wide roles in regulating agronomically important traits remain uncharacterized. Transcriptomic analyses of rice G-protein alpha subunit mutant (rga1) revealed 2270 differentially expressed genes (DEGs) including those involved in C/N and lipid metabolism, cell wall, hormones and stress. Many DEGs were associated with root, leaf, culm, inflorescence, panicle, grain yield and heading date. The mutant performed better in total weight of filled grains, ratio of filled to unfilled grains and tillers per plant. Protein–protein interaction (PPI) network analysis using experimentally validated interactors revealed many RGA1-responsive genes involved in tiller development. qPCR validated the differential expression of genes involved in strigolactone-mediated tiller formation and grain development. Further, the mutant growth and biomass were unaffected by submergence indicating its role in submergence response. Transcription factor network analysis revealed the importance of RGA1 in nitrogen signaling with DEGs such as Nin-like, WRKY, NAC, bHLH families, nitrite reductase, glutamine synthetase, OsCIPK23 and urea transporter. Sub-clustering of DEGs-associated PPI network revealed that RGA1 regulates metabolism, stress and gene regulation among others. Predicted rice G-protein networks mapped DEGs and revealed potential effectors. Thus, this study expands the roles of RGA1 to agronomically important traits and reveals their underlying processes."
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Authors: Hsing-Yi Cho, Mei-Yi Chou, Hsiu-Yin Ho, Wan-Chieh Chen and Ming-Che Shih.
Science Advances (2022)
One-sentence summary: A noncanonical ethylene signaling pathway triggers GCN2 to modulate translation dynamics in Arabidopsis during submergence.
Abstract: "General translational repression is a key process that reduces energy consumption under hypoxia. Here, we show that plant stress-activated general control nonderepressible 2 (GCN2) was activated to regulate the reduction in polysome loading during submergence in Arabidopsis. GCN2 signaling was activated by ethylene under submergence. GCN2 activity was reduced in etr1-1, but not in ein2-5 or eil1ein3, under submergence, suggesting that GCN2 activity is regulated by a noncanonical ethylene signaling pathway. Polysome loading was not reduced in ein2-5 under submergence, implying that ethylene modulates translation via both EIN2 and GCN2. Transcriptomic analysis demonstrated that EIN2 and GCN2 regulate not only general translational repression but also translational enhancement of specific mRNAs under submergence. Together, these results demonstrate that during submergence, entrapped ethylene triggers GCN2 and EIN2 to regulate translation dynamics and ensure the translation of stress response proteins."
Authors: Debabrata Panda and Jijnasa Barik.
Rice Science (2021)
Abstract: "Flooding is one of the most hazardous natural disasters and a major stress constraint to rice production throughout the world, which results in huge economic loss. Approximately one-fourth of the global rice crops (approximately 40 million hectares) are grown in rainfed lowland plots that are prone to seasonal flooding. A great progress has been made during last two decades in our understanding of the mechanisms involved in adaptation and tolerance to flooding/submergence in rice. In this review, we summarized the physiological and molecular mechanisms that contribute to tolerance of flooding/submergence in rice. We also covered various features of flooding stress with special reference to rice plants, viz. different types of flooding stress, environmental characterisation of flood water, impact of flooding stress on rice plant and their morphological, physiological and metabolic responses under flooding. A brief discussion on the tolerance mechanism in rice exhibited to different types of flooding will be focused for the future crop improvement programme for development of flooding tolerant rice variety."
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