G-protein βγ subunits determine grain size through interaction with MADS-domain transcription factors in rice

Abstract

The simultaneous improvement of grain quality and yield of cereal crops is a major challenge for modern agriculture. Here we show that a rice grain yield quantitative trait locus qLGY3 encodes a MADS-domain transcription factor OsMADS1, which acts as a key downstream effector of G-protein βγ dimers. The presence of an alternatively spliced protein OsMADS1lgy3 is shown to be associated with formation of long and slender grains, resulting in increases in both grain quality and yield potential of rice. The Gγ subunits GS3 and DEP1 interact directly with the conserved keratin-like domain of MADS transcription factors, function as cofactors to enhance OsMADS1 transcriptional activity and promote the co-operative transactivation of common target genes, thereby regulating grain size and shape. We also demonstrate that combining OsMADS1lgy3 allele with high-yield-associated dep1-1 and gs3 alleles represents an effective strategy for simultaneously improving both the productivity and end-use quality of rice.

Control of grain size by G protein signaling in rice

“…All these rice G protein subunits are involved in grain size regulation (Ashikari et al ; Fujisawa et al ; Fan et al ; Huang et al ; Zhou et al ; Trusov et al ; Liu et al ; Sun et al ). Loss of function of RGA1 results in small grains (Ashikari et al ; Fujisawa et al ), while overexpression of a constitutively active RGA1 increases grain length (Oki et al ), indicating that RGA1 positively regulates grain length.…”

“…Suppression of RGB1 using RNA interference (RNAi) technology leads to small grains (Utsunomiya et al ; Sun et al ). Interestingly, overexpression of RGB1 also reduces grain size (Liu et al ). Thus, it seems that appropriate expression level of RGB1 is critical for normal grain growth.…”

“…DEP1 corresponds to a major QTL for panicle shape and nitrogen use efficiency (Huang et al ; Zhou et al ; Sun et al ). DEP1 also regulates grain size (Liu et al ; Sun et al ). Overexpression of wild‐type DEP1 allele leads to large grains (Sun et al ).…”

“…Overexpression of dep1 leads to small grains, like those observed in DEP1 ‐RNAi lines (Sun et al ). Thus, dep1 has been recently recognized as a dominant‐negative allele (Sun et al ), although dep1 is proposed as the gain‐of‐function allele in several studies (Yi et al ; Sun et al ; Liu et al ).…”

“…Besides the three atypical Gγs (GS3, DEP1, and GGC2), the other two Gγs (RGG1 and RGG2) also regulate grain size (Liu et al ). Overexpression of RGG1 and RGG2 results in small grains (Liu et al ), suggesting that RGG1 and RGG2 restrict grain growth. Recently, it has been shown that loss of function of RGG2 increases grain size (Miao et al ).…”