Virus-induced gene silencing (VIGS) analysis shows involvement of the LsSTPK gene in lettuce (Lactuca sativaL.) in high temperature-induced bolting

To determine the effect of the serine/threonine protein kinase (STPK) gene on leaf lettuce bolting, we utilized virus-induced gene silencing (VIGS) using the TRV vector to silence the target gene. The ‘GB30ʹ leaf lettuce cultivar was the test material, and the methods included gene cloning, bioinformatics analysis, quantitative real-time PCR (qRT-PCR) and VIGS. LsSTPK, was cloned from the ‘GB30ʹ leaf lettuce cultivar via reverse transcription-polymerase chain reaction (RT-PCR). qRT-PCR analysis showed that the expression of LsSTPK in the stem of leaf lettuce was significantly greater than that in the roots and leaves, and after high-temperature treatment, the gene expression in the stems in the experimental group was markedly lower than that in the control groups. Following LsSTPK silencing via the VIGS method, the stem length in the treatment group was significantly greater than that in the blank and negative control groups, and the contents of auxin (IAA), GA3 and abscisic acid (ABA) in the treatment group were greater than those in the other two groups. Flower bud differentiation occurred in the treatment group but not in the control group. The above findings suggested that LsSTPK inhibits the bolting of leaf lettuce under high-temperature conditions.