Mechanisms Of Nucleotide Transferase Participating In Arabidopsis Flowering Regulation And Response To Abiotic Stress In Rice

Nucleotidyl transferase protein?NTP?can modify the 3' ends of the mature small RNAs,leading to their stabilization or degradation.The first two plant NTPs?HESO1 and URT1?were identified in Arabidopsis.According to our previous results,they can uridylate the 3' terminal nucleotide of miRNAs in hen1 mutant,resulting in their degradation,thus regulating the accumulation of their target genes.However,ntp mutants do not lead to any phenotypic variations in normal conditions.Thus,NTPs might involve in some specific conditions such as plant developmental mode transition or stress tolerance.Base on the known functions of NTPs,we wondered whether HESO1 and URT1,which have the function of uridylating the 3' terminal nucleotide of miRNAs,can also modify the 3' ends of mRNAs.We constructed the mRNA libraries of heso1 and heso1urt1 mutants,high-throughput sequencing results showed that some Oleosin genes are differentially expressed in heso1 and heso1urt1 mutants.It has been reported that Oleosin genes are commonly expressing in plant seeds and specific flowering stages.Thus,the flowering time of heso1 and urt1 mutants had been observed.heso1 and urt1 mutants showed that they had early-flowering phenotype.We also confirmed the phenotype with comparing the rosette leaves numbers of the mutants and the control,and overexpressing HESO1 in Arabidopsis.In order to analyze the flowering pathways which HESO1 and URT1 might be involved in,we studied the expressions of different floral genes in heso1 and urt1.We found the expressions of FRI and SOC1 were obviously higher in heso1 and urt1 mutants than those in wild type Arabidopsis?Col?under long day and short day conditions.Further studies will be carried out to investigate the involvement of HESO1 and URT1 in flowering control.In addition,we searched the protein database of Oryza sativa,Glycine max,Sorghum bicolor,Solanum lycopersium,Gossypium spp and Brassica rapa for putative NTPs by running the Hmmer 3.0 with the core domain.Through the phylogenetic analysis of NTPs,we found that NTP were contained in diverse plant species.NTPs from these plant species showed highly homologous.Thirteen putative NTPs in Oryza sativa have been identified.The sequences,number of introns,chromosomal location of each NTP genes,as well as the predicted amino acid lengths,predicted molecular weights,and predicted pI of each OsNTPs in rice had been studied.We found that the OsNTPs had different acid-base properties.All the OsNTPs had the core domain NTP_transf₂,which was commonly located in the Nterminal of the genes.In addition,some of the OsNTPs had the PAP_assoc domain which located in the C-terminal of the genes.Results from RT-PCR showed that the OsNTP genes were differentially expressed in different developmental stages or tissues.Trough the analysis of cis-acting elements in the promoter region of NTP genes,we found some of the genes contained the tolerance-related cis-acting elements.Promoter analysis result was validated by examining the expression levels of the NTP genes under abiotic stress treatments.Some of the OsNTPs were induced by salt,drought or cold stresses.This study suggests the NTPs which are involved in small RNA metabolic pathways might play roles in plant stress resistance.