Analysis Of Expression Characteristics Of Potato StSl-1 Gene Induced By Ralstonia Solanacearum

Potato(Solanum tuberosum)is an important staple food and cash crop in many countries.Potato is one of the hosts for phytopathogenic bacterium Ralstonia solanacearum causing bacterial wilt disease in more than 250 plant species worldwide.In the process of growth and production,Potato plants will encounter a variety of stress environments such as cold,heat,drought and salt.These factors have significant effects on potato cultivation.To study the molecular mechanism of potato disease resistance is the key to maintain and improve potato yield.In higher plants,Scarecrow-like protein(SCL)is a transcription factor belonging to the GRAS family.SCL can regulate root growth and cell cycle,and can also resist environmental stress.SCL,as a transcription factor,can encode and participate in plant information transmission and signal transduction.Plant-specific SCL transcription factors regulate plant development and participate in stress resistance.However,up to now,there are few studies on SCL gene in potato.In this work,a full-length cDNA sequence of Scarecrow-like21(SCL21)gene,named StSl-1,was obtained from potato(genotype ED13,resistant aganst bacterial wilt)inoculated with R.solanacearum and the expression patterns induced by the plant pathogen and by three phytohormes salicylic acid(SA),methyl jasmonate(MeJA)and abscisic acid(ABA)were analyzed by qRT-PCR.In situ hybridization technues were used to analyze the tissue and subcellular localization.The main results are as follows:Sequence analysis showed that the StSl-1 gene was composed of 2,139 bp nucleotides.The amino acid sequences of StSl-1 protein were highly similar to that of homologous SCL21 in potato species and other Solanaceae plants.The gene ecpression detedcted by qRT-PCR showed that the StSl-1 gene was expressed rapidly and continuously after innoculated by R.solanacearum and the expression level increased significantly at 12 to 36 hours after inoculation.After the inoculation of 36 hours internal reference genes and the control group were homogenized,the expression level of StSl-1 gene was 1.6 fold.Potato seedlings were treated with plant hormones.The results showed that these exogenous hormones upregulated StSl-1 in varying degrees.It was found that StSl-1 was involved in SA,MeJA and ABA signaling pathways.There were differences in the induced expression patterns of the three plant hormones.After the internal reference gene was homogenized with the control group,the relative expression of StSl-1 gene was about 2 fold,6 fold,and 7 fold,that is,ABA could strongly stimulate the expression of StSl-1 gene.The results of three test plants showed that the expression level of StSl-1 gene was the highest after induced by ABA.The StSl-1transcripts induced by ABA and MeJA decreased to a certain extent after the peak of expression,and the expression of SA was always at a low level.Fluorescence in situ hybridization(FISH)was used to detect the expression of StSl-1gene and the results showed that the gene was mainly expressed in the vascular bundles of leaves and phloem of stems.Subcellular localization of the gene transiently expressed in tobacco showed that the StSl-1 proteins were mainly located in the nucleus.These results may be laid a foundation for further study of the function of SCL21 in potato.All of these results suggested that the StSl-1 gene of potato may be involved in the early interaction between potato and bacterial wilt,and may be involved in the resistance of potato to bacterial wilt through ABA-mediated signaling pathway.Its detailed molecular mechanism needs to be further studied.It is expected that the research in this field will help to deepen the understanding of the resistance mechanism of potato bacterial wilt.