No abstract

TGA is one of the members of TGACG sequence-specific binding protein family, which plays a crucial role in the regulated course of hormone synthesis as a stress-responsive transcription factor (TF). Little is known, however, about its implication in response to bacterial wilt disease in potato (Solanum tuberosum) caused by Ralstonia solanacearum. Here, we performed an in silico identification and analysis of the members of the TGA family based on the whole genome data of potato. In total, 42 StTGAs were predicted to be distributed on four chromosomes in potato genome. Phylogenetic analysis showed that the proteins of StTGAs could be divided into six sub-families. We found that many of these genes have more than one exon according to the conserved motif and gene structure analysis. The heat map inferred that StTGAs are generally expressed in different tissues which are at different stages of development. Genomic collinear analysis showed that there are homologous relationships among potato, tomato, pepper, Arabidopsis, and tobacco TGA genes. Cis-element in silico analysis predicted that there may be many cis-acting elements related to abiotic and biotic stress upstream of StTGA promoter including plant hormone response elements. A representative member StTGA39 was selected to investigate the potential function of the StTGA genes for further analysis. Quantitative real-time polymerase chain reaction (qRT-PCR) assays indicated that the expression of the StTGAs was significantly induced by R. solanacearum infection and upregulated by exogenous salicylic acid (SA), abscisic acid (ABA), gibberellin 3 (GA3), and methyl jasmonate (MeJA). The results of yeast one-hybrid (Y1H) assay showed that StTGA39 regulates S. tuberosum BRI1-associated receptor kinase 1 (StBAK1) expression. Thus, our study provides a theoretical basis for further research of the molecular mechanism of the StTGA gene of potato tolerance to bacterial wilt.

Cell wall glycine‐rich proteins (GRPs) play important roles in plant growth and development, as well as in the effective prevention of plant diseases. Although members of the GRP family have been identified in several plants, a comprehensive analysis of GRPs has not been reported in Solanaceae plants. In this study, 43 GRPs were identified from Solanum tuberosum (named StGRPs), Solanum lycopersicum, Capsicum annuum and Nicotiana attenuata. The comparative study of these GRPs showed that they were conservative in physical properties, structures of genes and motifs. The expression patterns of Solanum tuberosum StGRPs under biotic and abiotic stress were analysed and presented very diverse profiles in responding to ABA, IAA, GA3, high salinity, pathogen and heat stress. Some StGRPs were preferentially and specifically expressed during the development of petioles and tubers, in which the expression of StGRPs was more sensitive to ABA confirmed by qRT‐PCR analysis. The strongly up‐regulated expression of StGRP1 induced by Ralstonia solanacearum indicated the positive role involved in the resistance against the bacterial wilt pathogen. Tissue localization analyses by Digoxin/fluorescence in situ hybridization indicated that the expression of StGRP1 was vascular‐specific and associated with cell wall thickening in vascular bundles and interfascicular fibres after R. solanacearum inoculation. These findings may provide a new insight into the roles of GRPs in adaptation to diverse stresses and in resistance to R. solanacearum in potatoes.