| Outline of Annual Research Achievements |
Our comparative analyses of the max2 single, cytokinin (CK) ahk2 ahk3 double and ahk2 ahk3 max2 triple mutants during plant growth and development demonstrated that the CK and MAX2 pathways regulate primary root growth, root hair elongation and rosette leaf radius in opposite manner. CK pathway negatively regulates primary root and root hair elongation, but positively rosette leaf radius. Conversely, MAX2 pathway plays positive role in primary root and root hair elongation, but negatively controls rosette leaf radius. Additionally, both two pathways have positive effects on shoot elongation, seed yield and callus induction, but negative effects on shoot branching and seed size. CK signaling has a major role in controlling leaf size but a minor role in regulating leaf shape and natural senescence, whereas the reverse trend was observed for MAX2 signaling. Importantly, we provided evidence for the interactive effects of CK and MAX2 pathways on primary root growth, hypocotyl elongation and shoot branching. However, these two pathways might independently affect root hair elongation, rosette leaf radius, early and late leaf development, plant height, senescence, seed size, seed yield and callus formation. Our findings provide not only evidence for the involvement of MAX2 in regulating callus formation, seed size and seed yield, but also a better understanding of the relationship between CK and MAX2 signaling pathways in many key developmental processes across a plant's life.
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| Strategy for Future Research Activity |
We will study the function of the strigolactone (SL)-specific receptor D14 in plant adaptation to drought in comparison with the karrikin (KAR)-specific receptor KAI2 following the detailed methods published in the below papers. The d14 and kai2 single and d14 kai2 double mutants will be compared in various drought tolerance, physiological, biochemical and molecular assays to identify the specific mechanisms underlying D14 and KAI2 functions in Arabidopsis response to drought.
(1) Li W, Nguyen KH, Chu HD, Ha CV, Watanabe Y, Osakabe Y, Leyva-Gonzalez MA, Sato M, Toyooka K, Voges L, Tanaka M, Mostofa MG, Seki M, Seo M, Yamaguchi S, Nelson DC, Herrera-Estrella L, Tran LS (2017). PLoS Genet 13:e1007076.
(2) Nguyen KH, Mostofa MG, Li W, Ha CV, Watanabe Y, Le DT, Thao NP, Tran LS (2018). Environ Exp Bot 151:12-20.
(3) Nishiyama R, Watanabe Y, Fujita Y, Le DT, Kojima M, Werner T, Vankova R, Yamaguchi-Shinozaki K, Shinozaki K, Kakimoto T, Sakakibara H, Schmulling T, Tran LS (2011). Plant Cell 23:2169-83.
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