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Study on rice Histone Deacetylase 2 (HD2)family in regulating flowering time and abiotic stress tolerance
- Rice is a facultative short-day (SD) plant in which flowering is induced under SD conditions or by other environmental factors and internal genetic programs. Overexpression of Histone Deacetylase 701 (HDT701)accelerates flowering in hybrid rice. In this study, I report that mutants defective in HDT701 flowered late under both SD and long-day conditions. Expression levels of florigens Heading date 3a (Hd3a) and Rice Flowering Locus T1 (RFT1), and their immediate upstream floral activator Early heading date 1 (Ehd1),were significantly decreased in the hdt701 mutants, indicating that HDT701 functions upstream of Ehd1 in controlling flowering time. Transcript levels of OsINDETERMINATE SPIKELET 1 (OsIDS1), an upstream repressor of Ehd1, were significantly increased in the mutants while those of OsGI and Hd1 were reduced. Chromatin-immunoprecipitation assays revealed that HDT701 directly binds to the promoter region of OsIDS1. These results suggest that HDT701induces flowering by suppressing OsIDS1. Being sessile organisms, plants need to adapt to unfavorable environmental stresses to modulate their optimal growth and development. When plants are exposed to abiotic stresses, a large number of genes are triggered and synchronized to optimize their growth under diverse abiotic stresses. Expression of HDT701 is regulated by abiotic stress conditions and HDT701 overexpressing transgenic rice shows higher tolerance to osmotic and salt stresses at the seedling stage as previously reported. Here, I report that hdt701 mutant seedlings displayed increased sensitivity to both salt and osmotic stresses. Expression levels of Oryza sativaPhytoene Synthase 3 (OsPY3)and 9-cis-epoxycarotenoid dioxygenase 4 (NCED4), ABA biosynthesis genes induced by salt stress , and STRESS-RESPONSIVE NAC 1 (SNAC1), anabiotic stress inducible gene, were significantly decreased in the mutants , revealing that HDT701 functions upstream of them in regulating abiotic stresses. The expression of Oryza sativa respiratory burst oxidase homolog I (OsrbohI), an NADPH oxygenase gene that is responsible for the production of reactive oxygen species (ROS), was also remarkably suppressed in the mutant seedlings while that of OsWRKY45, an upstream suppressor of SNAC1 and NCED4, was dramatically induced. These resulting data suggest that HDT701 might enhance the salt and osmotic stress tolerance of rice by suppressing OsWRKY45 as well as through ROS pathway by enhancing OsrbohI.
Antt Htet Wai