Diversity of Secretion System Apparatus in Tomato Wilt Causing Ralstonia solanacearum Strains: a Comparative Analysis Using in-silico Approach

Ralstonia solanacearum (Rs) species is the leading cause of bacterial wilt disease in a wide range of host plants worldwide. In the present study, secretion system analysis of five tomato pathogenic Rs strains was carried out in-silico. This paper describes a new protocol to identify the secretion system components i.e. SSCs (T1SS-T6SS, Flg, T4P, and Tad-Tat). A total of 865 SSCs were identified using the new protocol. Contributions of SSCs into core-secretion system apparatus (i.e. SSA) were also studied. Synteny was discovered among the secretion system apparatus (SSA) where relative frequency of SSCs to core-SSA is high (>20%) which includes T1SS, T2SS, T5SS, T4P, and Tad-Tat, but excludes T3SS, T4SS, and Flg. To the best of our knowledge, this is the first report indicating that during the evolution of Rs, most of the secretion system apparatus (T1SS, T2SS, T5SS, T4P, and Tad-Tat) were highly conserved and came from a single ancestor, while T3SS and T6SS may have arrived later, probably from horizontal gene transfer.