DDG1 and G Protein α Subunit RGA1 Interaction Regulates Plant Height and Senescence in Rice(Oryza sativa)

Many studies have already shown that dwarfism and moderate delayed leaf senescence positively impact rice yield,but the underlying molecular mechanism of dwarfism and leaf senescence remains largely unknown.Here,using map-based cloning,we identified an allele of DEP2,DDG1,which controls plant height and leaf senescence in rice.The ddg1 mutant displayed dwarfism,short panicles,and delayed leaf senescence.Compared with the wild-type,ddg1 was insensitive to exogenous gibberellins(GA)and brassinolide(BR).DDG1 is expressed in various organs,especially in stems and panicles.Yeast two-hybrid assay,bimolecular fluorescent complementation and luciferase complementation image assay showed that DDG1 interacts with theα-subunit of the heterotrimeric G protein.Disruption of RGA1 resulted in dwarfism,short panicles,and darker-green leaves.Furthermore,we found that ddg1 and the RGA1 mutant was more sensitive to salt treatment,suggesting that DDG1 and RGA1 are involved in regulating salt stress response in rice.Our results show that DDG1/DEP2 regulates plant height and leaf senescence through interacting with RGA1.

Characterization of a Novel Weak Allele of RGA1/D1 and Its Potential Application in Rice Breeding

Semi-dwarfing improves the lodging resistance and yield of rice,and the vast majority of modern rice varieties harbor the sd1 allele to decrease plant height,resulting in reduced genetic diversity and negative agronomic traits.Thus,exploring alternative sources of dwarfism is imperative for rice breeding.Here,we identified a novel RGA1 allele,d1-w,from a local indica variety Xiaolixiang(XLX)using a map-based cloning approach.Compared with other rice varieties,RGA1 in XLX contained a unique single nucleotide polymorphism that resulted in an additional transcript and reduced functional RGA1 transcript level.The RGA1 from Nipponbare was introduced into XLX to estimate the value of d1-w in rice breeding.Compared with transgenic XLX plants(XLX^(D1)),XLX exhibited reduced plant height,increased stem strength,lower reactive oxygen species accumulation,delayed senescence,stronger photosynthesis,higher grain yield and quality(including external,milling and nutritional qualities),and enhanced resistance to drought and Rhizoctonia solani.Therefore,we proposed that the d1-w allele has potential as an excellent dwarfism resource for rice breeding.