Poaceae Orthologs of Rice OsSGL, DUF1645 Domain-Containing Genes, Positively Regulate Drought Tolerance, Grain Length and Weight in Rice

Abstract BackgroundGrain yield is a polygenic trait influenced by environmental and genetic interactions at all growth stages of the cereal plant. However, the molecular mechanisms responsible for coordinating the trade-off or cross-talk between these traits remain elusive.ResultsWe characterized the hitherto unknown function of four STRESS_tolerance and GRAIN_LENGTH (OsSGL) Poaceae ortholog genes, all encoding DUF1645 domain-containing proteins, in simultaneous regulation of grain length, grain weight, and drought stress-tolerance in rice. In normal growth conditions, the four ortholog genes were mainly expressed in the developing roots and panicles of the corresponding species. Over-expressing or heterologous high-level expressing Poaceae OsSGL ortholog genes conferred remarkably increased grain length, weight, and seed setting percentage, as well as significantly improved drought-stress tolerance in transgenic rice. Microscopical analysis also showed that the transgene expression promoted cell division and development. RNA-seq and qRT-PCR analyses revealed 73.8% (18,711) overlapped DEGs in all transgenic plants. Moreover, GO and KEGG analyses of different comparisons revealed that the key DEGs participating in drought stress-response belonged to hormone (especially auxin and cytokinin) pathways, and signaling processes were apparently affected in the young panicles. ConclusionTogether, these results suggest the four OsSGL orthologs perform a conserved function in regulating stress-tolerance and cell growth by acting via a hormone biosynthesis and signaling pathway. It may also induce a strategy for tailor-made crop yield improvement.