Identification of phosphorus starvation inducible SnRK genes in tomato (Solanum lycopersicum L.)

The sucrose non-fermenting 1-related protein kinases (SnRKs) mediate plant signalling pathways in response to different cues by phosphorylating target proteins. While full complement of these genes has been reported in several families, such information remains obscure in Solanaceae to date. Through a genome-wide identification approach, we report 40 SnRK members in the tomato genome. Multiple alignments and phylogenetic analysis grouped the identified genes in SnRK1, SnRK2, and SnRK3 subfamilies. SnRK1 subfamily comprises only two members, whereas SnRK3 being the largest category, is constituted by 30 members in tomato. Ten members of the SnRK3 subfamily are present in four tandemly duplicated chromosomal blocks. Transcript profiling of these genes during tomato development identified SlSnRK2.9 and SlSnRK3.3 with root-specific and SlSnRK2.7b with ripening-preferential mRNA abundance. The mRNA profiling of these genes by RNA-sequencing and qPCR revealed that SlSnRK3.10a, SlSnRK3.15a, and SlSnRK3.26 are activated at varying levels under phosphate (Pi) starvation. In-silico analysis anticipated a common set of proteins interacts with the selected phosphorus starvation inducible (PSI) SlSnRK genes. Overall, the present study identifies a set of PSI SnRKs in tomato and provides a comprehensive framework for their functional characterization in Solanaceae in the future.