Drought is a major environmental factor that limits plant growth and crop productivity. Genetic engineering is an effective approach to improve drought tolerance in various crops, including rice (Oryza sativa). Functional characterization of relevant genes is a prerequisite when identifying candidates for such improvements. We investigated OsSGL (Oryza sativa Stress tolerance and Grain Length), a novel DUF1645 domain-containing protein from rice. OsSGL was up-regulated by multiple stresses and localized to the nucleus. Transgenic plants over-expressing or hetero-expressing OsSGL conferred significantly improved drought tolerance in transgenic rice and Arabidopsis thaliana, respectively. The overexpressing plants accumulated higher levels of proline and soluble sugars but lower malondialdehyde (MDA) contents under osmotic stress. Our RNA-sequencing data demonstrated that several stress-responsive genes were significantly altered in transgenic rice plants. We unexpectedly observed that those overexpressing rice plants also had extensive root systems, perhaps because transcript levels were altered for auxin- and cytokinin-associated genes. These results suggest that the mechanism by which OsSGL confers greater drought tolerance is due to the modulated expression of stress-responsive genes, higher accumulations of osmolytes, and enlarged root systems.

This study reveals a novel regulatory mechanism that links the versatile receptor kinase FERONIA with plant C/N responses.

Abiotic stress seriously affects the yield of rice (Oryza sativaL.). Grain yield in rice is multiplicatively determined by the number of panicles, number of grains per panicle, and grain weight. Here, we describe the molecular and functional characterization ofSTRESS_tolerance and GRAIN_LENGTH (OsSGL), a rice gene strongly up-regulated by a wide spectrum of abiotic stresses.OsSGLencodes a putative member of the DUF1645 protein family of unknown function. Overexpression ofOsSGLsignificantly altered certain development processes greatly and positively affecting an array of traits in transgenic rice plants, including increased grain length, grain weight and grain number per panicle, resulting in a significant increase in yield. Microscopical analysis showed that the enhancedOsSGLexpression promoted cell division and grain filling. Microarray and quantitative real-time PCR (qRT-PCR) analyses revealed that a large number of genes involved in stress-response, cell cycle and cytokinin signaling processes were induced or suppressed inOsSGL-overexpressing plants. Together, our results suggest thatOsSGLmay regulate stress-tolerance and cell growth by acting via a cytokinin signaling pathway. This study not only contributes to our understanding of the underlying mechanism regulating rice stress-tolerance and grain length, but also provides a strategy for tailor-made crop yield improvement.