Molecular characterization of StpkaC2 and expression patterns of both PKA-c isoforms during the invasive growth of Setosphaeria turcica

Abstract

In order to clarify the roles of different protein kinase A (PKA) isoforms during the pathogenesis, a gene coding the catalytic subunit of PKA (PKA-c) of S. turcica was predicted from the genome database. In addition, the transcriptional profile during the formation of the invasive structure was studied through qPCR. Results showed that the StpkaC2 gene harbored an ORF of 1209 bp that encoded the PKA-c with its 402 amino acid residues. Phylogenetic analysis revealed that StpkaC2 and StpkaC1 belonged to different clusters. Gene expression patterns of StpkaC2 during germ tube formation was 2.2 times higher than that at the conidial phase (control), but decreased slightly during appressoria formation and mature stages of infection. During the intrusive filament formation stage, gene expression increased to levels that were 4.2 times higher than the control. Instead, the mRNA levels of StpkaC1 were similar at 0, 3, 6 and 12 hpi. However, at 24 hpi, gene expression increased to levels that were 3.2 times higher than that control. Results suggest that StpkaC2 is more active than StpkaC1 during germ tube and appressoria formation, and mature stages. Conversely, both StpkaC2 and StpkaC1 are important during the invasive hyphae formation stage.