Biological Function Analysis Of OsSRT1 In Rice

Sirtuin protein family members are histone deacetylases(HDAC),and exsit in various organisms ranging from bacteria to human beings.This group of enzymes are NAD~+-dependent HDACs,and highly conserved in different organisms.Recent studies have shown that Sirtuin proteins play essential roles in many aspects of biological processes including chromatin silencing,cell division,life-span control,cell apoptosis,and energy control.There are two Sirtuin homologous genes named OsSRT1 and OsSRT2 in rice.As a member of the SIR2 family of plant HDACs,the biological function and the underlying molecular mechanisms of OsSRT1 is still need to be characterized.Previous studies showed that OsSRT1 is probably associated with energy metabolism.And the functional characterization of OsSRT1 could provide key information to know how energy metabolism regulates gene expression.The main energy metabolism in leaves is photosynthesis.In this study,the biological function and regulatory role of OsSRT1 playing in photosynthesis were investigated in rice.The main results are as follows:1.The intact ORF of OsSRT1 was cloned from rice japonica variety Zhonghua11(ZH11).By bioinformatics analysis,we found that OsSRT1 is located in nucleus.Phylogenetic analysis showed that OsSRT1 is highly homologous to maize ZmSIR2,Arabidopsis AtSRIR2-1,as well as human SIRT6 and SIRT7.2.Western blot analysis showed that the level of H3K9 acetylation was decreased in OsSRT1-overexpression lines and increased in OsSRT1-antisense lines,indicating that the expression of OsSRT1 directly affects the level of H3K9 acetylation.3.Phenotypic observation showed that OsSRT1-antisense plants exibited delayed development,and the leaves had obvious injury spots caused by the increase of reactive oxygen species proved by NBT staining.The increased content of lignin in leaves resulted in the increased mechanical support in OsSRT1-antisense plants.We also found that the contents of three elements of sulpher(S),phosphor(P)and potassium(K)were decreased in OsSRT1-antisense plants.4.The Y(I)and ETR(I)were significantly decreased in in OsSRT1-antisense plants determined by the detection assay of chlorophyll fluorescence,indicating the decreased photosyntheticefficiency.Inaddition,thephotosyntheticefficiencyof OsSRT1-overexpression plants was improved,which resulted in the increased yield.5.The putative target genes regulated by OsSRT1 were screened by transcripome sequencing of wild-type ZH11,OsSRT1-overexpression lines and OsSRT1-antisense lines,and nine genes were selected and verified by qRT-PCR analysis.As a results,one out of five selected genes was invlolved in the regulation of photosynthesis.The results obtained by this study provide a basis for further study on the molecular mechanism of OsSRT1 in the regulation of rice growth and development by regulating photosynthesis.