Functional Analysis Of OsSET34,a Gene Histone Methyltransferase In Rice(Oryza Sativa L.)

The heading date of rice not only determines the variety of seasonal adaptability and the grown regions of rice cultivar,but also an important transition from the growth stage to the reproductive growth stage.Rice as one of the world's four largest food crops is the annual grass plants and a short day model plant.This work is based on a previous study which identified very late heading date mutant ah(t)from Nanjing 35 radiation mutagenesis(Wu,2013).ah(t)was located in ninth rice chromosomes via map-based cloning approach.Sequence analysis found the difference of OsSET34 gene between wild type and mutant.OsSET34 encodes a histone H3 methyltransferase.Nanjing 35 was approximately 100 days to heading,but ah(t)was 150 days to heading after germination in Nanjing natural long day conditions.Grain length and width had no difference between the mutant and the wild type,but 1000-grain weight and grain thickness had difference.We found that OsSET34 and SDG724(Sun,2012)may be multiple alleles by reviewing literature.In order to verify the effects of OsSET34 and SDG724,we analyse the expression of SDG724 and other heading date genes of Nanjing 35 and ah(t)in different day length treatment.Results showed the expression of heading date genes did not change significantly,which was similar in SDG724.OsSET34 showed a constitutive expression,which leaf and leaf sheath had high expression and root had slightly lower expression.The subcellular localization of OsSET34 protein was localized in the nucleus.In addition,we found that the Nanjing 35 and ah(t)had differences in seed germination rate and ah(t)had sensitivity enhancement to exogenous GA and ABA in seed germination rate.In the treatment of 10?M GA3,we analysed the expression of dormancy related genes after seed germination in Nanjing 35 and ah(t)and found that the GA pathway between Nanjing 35 and ah(t)was not affected.In the treatment of GA3,the expression of DOG1-1 and DOG1-3 in Nanjing 35 was down-regulated and the expression of DOG1-1 and DOG1-3 had no significant difference in ah(t).The expression of alpha amylase gene in Nanjing 35 was up-regulated,which had no difference in ah(t).These differences may be due to methylation regulation.There were differences of seed germination rate between Nanjing 35 and ah(t),which may ah(t)was significantly difference at the seeding stage,especially the difference was maximal in the fifth day.The auxin signal transduction pathway related genes were analyzed by qRT-PCR.There are rice two type genes in response to auxin signaling pathway Aux/IAA and ARF,which are known to have 31 Aux/IAA genes and 26ARF genes.The expression of most signal transduction genes were up-regulated in the fifth day at the seedling stage in the mutant ah(t).This study demonstrated that the OsSET34 regulated the Auxin signaling pathway to influence the growth of seedlings.This study reports the function of OsSET34 in rice and discusses that the methylation modification not only controls the rice heading date,but also may be involved in the regulation of germination rate and auxin signal transduction pathway.This work lays the foundation for studying the rice seed dormancy from the methylation level.