Abstract
Maintaining stable, high yields under fluctuating environmental conditions is a long-standing goal of crop improvement but is challenging due to internal trade-off mechanisms, which are poorly understood. Here, we identify ARGONAUTE2 (AGO2) as a candidate target for achieving this goal in rice (Oryza sativa). Overexpressing AGO2 led to a simultaneous increase in salt tolerance and grain length. These benefits were achieved via the activation of BIG GRAIN3 (BG3), encoding a purine permease potentially involved in cytokinin transport. AGO2 can become enriched on the BG3 locus and alter its histone methylation level, thus promoting BG3 expression. Cytokinin levels decreased in shoots but increased in roots of AGO2-overexpressing plants. While bg3 knockout mutants were hypersensitive to salt stress, plants overexpressing BG3 showed strong salt tolerance and large grains. The knockout of BG3 significantly reduced grain length and salt tolerance in AGO2-overexpressing plants. Both genes were transcriptionally suppressed by salt treatment. Salt treatment markedly increased cytokinin levels in roots but decreased them in shoots, resulting in a hormone distribution pattern similar to that in AGO2-overexpressing plants. These findings highlight the critical roles of the spatial distribution of cytokinins in both stress responses and grain development. Therefore, optimizing cytokinin distribution represents a promising strategy for improving both grain yield and stress tolerance in rice.
Highlights
14! One determinant of grain yield, grain weight, is affected by grain size and 15! grain filling
OsABCG18 was recently shown to direct 47! cytokinin transport from root to shoot in rice (Zhao et al, 2019), playing a 48! similar role to its ortholog ABCG14 in Arabidopsis (Arabidopsis thaliana) (Ko et 49! al., 2014; Zhang et al, 2014)
Knockout or overexpression of OsABCG18 50! resulted in pleiotropic developmental phenotypes including altered grain size 51! (Zhao et al, 2019). These findings suggest that cytokinin transport plays an 52! important role in plant growth and development
Summary
Brassinosteroids are involved in regulating plant resistance to stress, 27! Family member (OsPUP4), regulates leaf length and grain size in rice Cytokinin transport from root to shoot in rice (Zhao et al, 2019), playing a 48! (Zhang et al, 2015) In addition to these canonical mechanisms, AGO1 60! Arabidopsis (Liu et al, 2018a) Responses to stimuli (Liu et al, 2018a), and AGO2 is involved in plant immunity 67! Loss-of-function of AGO7 resulted in failed shoot development, while plants 77! AGO17 improves grain size and plant growth by promoting the accumulation of 81! Crucial role in stress responses as well as grain development. Optimizing 88! cytokinin distribution patterns in plants represents a promising strategy for 89! simultaneously enhancing grain yield, grain quality, and stress resistance, as 90! exemplified by AGO2-overexpressing plants
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
