Differential Space-Time Expression of StLTPb1 Gene Between Resistant and Susceptible Potato Genotypes in Response to Ralstonia solanacearum

Abstract

This study is to investigate the role of lipid transfer protein ( LTP1) gene of potato ( Solanum tuberosum) in bacterial wilt ( Ralstonia solanacearum) resistance. A novel cDNA clone encoding nsLTP was isolated from cultivated potato ( Solanum tuberosum) infected with R. solanacearum by 5′-rapid amplification of cDNA ends (RACE). The temporal and spatial expression of StLTPb1 was studied during the early stages of potato- R. solanacearum interaction by reverse transcriptase PCR (RT-PCR) and Northern blotting. The sequence analysis of the cloned cDNA, named StLTPb1, showed 691 bp which encoded a type 1 nsLTP of 91 amino acids. Construction of a phylogenic tree showed that StLTPb1 is well conserved in the coding region with high identity at the amino acid level with other Solanaceae nsLTPs. The temporal and spatial expression of StLTPb1 was studied during the early stages of potato- R. solanacearum interaction. StLTPb1 transcription is induced faster and transcripts accumulate to higher concentrations in resistant compared with susceptible genotypes by the pathogen. Dominant differences in the pathogen-induced gene expression pattern between the upper and lower leaves and stems were observed within the same genotypes. In situ hybridization results showed that the StLTPb1 mRNA was localized in phloem cells of vascular tissues in potato leaf and stem tissues after pathogen infection. Salicylic acid, methyl jasmonate and abscisic acid could induce StLTPb1 gene expression without significant difference between the upper and lower tissues. These abiotic elicitors could produce a long-lasting effect on the StLTPb1 during early stages of potato- R. solanacearum interaction. Differential expression of StLTPb1 gene between resistance and susceptible potato genotypes in response to R. solanacearum suggests that this gene plays a key role in plant defense mechanisms.