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Although nonspecific lipid transfer proteins (nsLTPs) are widely expressed during plant defence responses to pathogens, their functions and regulation are not fully understood. In this article, we report the isolation of a cDNA for the new nsLTP, StLTPa7, from cultivated potato (Solanum tuberosum) infected with Ralstonia solanacearum. The cDNA was predicted to encode a type 1 nsLTP containing an N-terminal signal sequence and possessing the characteristic features of nsLTPs. A phylogenetic analysis showed that the encoded amino acid sequence of the nsLTP was similar to those of other previously reported plant nsLTPs, which contain a putative calmodulin-binding site consisting of approximately 12 highly conserved amino acid residues. The expression of the StLTPa7 gene was studied during the early stages of potato-R. solanacearum interaction using real-time quantitative polymerase chain reaction (qRT-PCR) and Northern analyses, and a complex calcium (Ca2+)-associated pattern of expression was observed with the following features: (i) transcripts of the StLTPa7 gene were systemically up-regulated by infection with R. solanacearum; (ii) the StLTPa7 gene was stimulated by salicylic acid, methyl jasmonate, abscisic acid and Ca2+; (iii) qRT-PCR showed that, during the early stage of R. solanacearum infection, nsLTP transcripts accumulated over a time course that paralleled that of Ca2+ accumulation, detected using environmental scanning electron microscopy and energy-dispersive X-ray (EDAX) spectrometry; and (iv) the Ca2+ channel blocker, ruthenium red, partially blocked R. solanacearum-induced StLTPa7 expression. This report represents the first use of EDAX analysis to establish a synchrony between Ca2+ accumulation and nsLTP expression in response to potato-R. solanacearum interactions. Collectively, these results suggest that StLTPa7 may be a pathogen- and Ca(2+)-responsive plant defence gene.

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. solanacea rum 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. solanacea rum 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.

A full-length cDNA of proteinase inhibitor gene with completed open reading frame of 116 amino acids was cloned from Ralstonia solanacearum (Rs) resistant potato leaves using the rapid amplification of cDNA ends (RACE) method and designated as StPI. BLAST search against NCBI showed that the StPI gene shared 89% identity with potato proteinase inhibitor I precursor in nucleotide and 74% in amino acid. Analysis of semi-quantitative RT-PCR indicated that this gene was induced by Rs as well as up-regulated by jasmonic acid (JA). The StPI gene expression reached the highest level during 6-12 h post Rs-inoculation or JA-treatment, and then leveled off. Moreover, this gene was strongly induced by JA and its mRNA accumulation increased more quickly than that of Rs-inoculation. The StPI gene may play a role in potato resistance against Rs. The induction of StPI by Rs invasion may have a similar signal transduction pathway with JA treatment.

Although nonspecific lipid transfer proteins (nsLTPs) are widely expressed during plant defence responses to pathogens, their functions and regulation are not fully understood. In this article, we report the isolation of a cDNA for the new nsLTP, StLTPa7, from cultivated potato (Solanum tuberosum) infected with Ralstonia solanacearum. The cDNA was predicted to encode a type 1 nsLTP containing an N‐terminal signal sequence and possessing the characteristic features of nsLTPs. A phylogenetic analysis showed that the encoded amino acid sequence of the nsLTP was similar to those of other previously reported plant nsLTPs, which contain a putative calmodulin‐binding site consisting of approximately 12 highly conserved amino acid residues. The expression of the StLTPa7 gene was studied during the early stages of potato–R. solanacearum interaction using real‐time quantitative polymerase chain reaction (qRT‐PCR) and Northern analyses, and a complex calcium (Ca(2+))‐associated pattern of expression was observed with the following features: (i) transcripts of the StLTPa7 gene were systemically up‐regulated by infection with R. solanacearum; (ii) the StLTPa7 gene was stimulated by salicylic acid, methyl jasmonate, abscisic acid and Ca(2+); (iii) qRT‐PCR showed that, during the early stage of R. solanacearum infection, nsLTP transcripts accumulated over a time course that paralleled that of Ca(2+) accumulation, detected using environmental scanning electron microscopy and energy‐dispersive X‐ray (EDAX) spectrometry; and (iv) the Ca(2+) channel blocker, ruthenium red, partially blocked R. solanacearum‐induced StLTPa7 expression. This report represents the first use of EDAX analysis to establish a synchrony between Ca(2+) accumulation and nsLTP expression in response to potato–R. solanacearum interactions. Collectively, these results suggest that StLTPa7 may be a pathogen‐ and Ca(2+)‐responsive plant defence gene.