Functional Study Of Tomato SlMYB86 Gene In Inflorescence Development And Abiotic Stress Responses

MYB transcription factors contain a large plant-specific gene family,which are involved in plant growth and development,biotic and abiotic stress responses.Currently,considerable progress has been made to unravel the diverse roles of MYB transcription factors in plants,but studies on MYB transcription factors mainly concentrated in Arabidopsis.As a model plant for scientific research,tomato(Solanum lycopersicum)is also an important vegetable crop.This inspired us to explore new members of the MYB gene family that may be involved in the regulation of plant reproductive development.In this research,the SlMYB86 gene was screened from tomato using bioinformatics methods.Then,we constructed the silence vector and transformed it into tomato through agrobacterium-mediated genetic transformation to study the function of the gene.The main research contents are as follows:We screened out the SlMYB86 gene by bioinformatics analysis and tomato database SGN,evolutionary tree analysis showed that SlMYB86 shared higher similarity with At MYB61.Promoter analysis of SlMYB86 exhibited that there were three low temperature response elements,a drought response element,three ABA response elements and three gibberellin-responsive-elements in its promoter.Gene expression pattern analysis showed high accumulation was observed in stem,followed by immature green fruits and flowers.In addition,under drought and salt stress,the expression of SlMYB86 was changed.The transcription level of SlMYB86 was induced by exogenous ABA,GA3,Me JA,IAA and ACC.Constructing SlMYB86 silence vector and transforming it into wild type(WT)tomato plants.SlMYB86-RNAi lines with the silencing efficiency over 90% were obtained.SlMYB86-RNAi plants had more inflorescence branches and more flowers compared with the WT.Meanwhile,there was no significant difference in fruit setting rate,which increased the yield per plant.The q RT-PCR results showed that the inflorescence development-related genes SOC1,AP2 a,FA,SP,and LFY were up-regulated in the apical bud of the SlMYB86-RNAi lines,while the expressions of the genes LS,WUS,S,and TMF were significantly reduced.The results suggested that SlMYB86 gene was involved in regulating tomato inflorescence development.However,yeast two-hybrid analysis showed that SlMYB86 was unable to interact with the proteins WUS,SOC1,and LFY.When treated with 100 m M Na Cl,the shoot and root lengths of SlMYB86-RNAi seedlings were significantly stronger than WT and the seedling weight was also significantly heavier.Secondly,there was no significant difference in germination rates between WT and SlMYB86-RNAi seeds without Na Cl treatment.With the increase of Na Cl concentration,seed germination rate of both were inhibited at 40 m M,60 m M and80 m M,but the seed germination rate of the silenced line was notably higher than WT seeds.Especially at 80 m M Na Cl,WT seeds did not germinate at all,but SlMYB86-RNAi seeds could still germinate.After high concentration of salt treatment,SlMYB86-RNAi T2 seedlings wilted more slowly than the WT.Examination of related physiological indicators found that the total chlorophyll content of SlMYB86-RNAi seedling leaves was higher,MDA(malondialdehyde)content were lower and relative conductivity were lower.The results of q RT-PCR showed that the expression of stress-related genes PR1,PR5,GME2,P5 CS,Cat1,Cat2,TAS14,and ER5 increased significantly in the roots of SlMYB86-RNAi seedlings.Meanwhile,the expression of stagnant green gene SlSGR1 was higher,and the expression levels of chlorophyll synthesis-related genes DCL,pas E1 and DHLH decreased faster in the leaves of SlMYB86-RNAi seedlings.These results indicated that SlMYB86-RNAi plants were more tolerant to salt stress.For drought resistance analysis of T2 generation seedlings of SlMYB86-RNAi lines,the results showed that the leaf water loss rate and MDA content of transgenic plants were significantly lower than that of WT,and relative water content and leaf total chlorophyll content were significantly higher than those of WT.In addition,the ABA content of SlMYB86-RNAi plants were significantly higher than WT plants when untreated.These results indicated that SlMYB86-RNAi seedlings were more tolerant to drought stress.For SlMYB86-RNAi seedling hormone sensitivity experiments,at 3 μM and 10 μM ABA,the transgenic seedlings had significantly shorter stem and root lengths than the WT,the weight of the seedlings was also significantly lighter than that of WT.When treated with 100 u M Yucasin and 100 u M Kyn respectively,the transgenic seedlings showed shorter stem lengths,no significant differences in root lengths,fewer lateral roots,and lighter seedlings compared to WT.These results indicated that silencing of SlMYB86 enhanced the sensitivity of tomato seedlings to ABA,Kyn and Yucasin.In summary,this article has initially explored the functions of SlMYB86 transcription factor in tomato inflorescence development and salt,drought stress in plants,which lays a theoretical foundation for further studying the molecular mechanism of SlMYB86 gene involved in inflorescence development and in response to abiotic stress.