Abstract
Drought is a major threat to agriculture production worldwide. Mitogen-activated protein kinases (MAPKs) play a pivotal role in sensing and converting stress signals into appropriate responses so that plants can adapt and survive. To examine the function of MAPKs in the drought tolerance of tomato plants, we silenced the SpMPK1, SpMPK2, and SpMPK3 genes in wild-type plants using the virus-induced gene silencing (VIGS) method. The results indicate that silencing the individual genes or co-silencing SpMPK1, SpMPK2, and SpMPK3 reduced the drought tolerance of tomato plants by varying degrees. Co-silencing SpMPK1 and SpMPK2 impaired abscisic acid (ABA)-induced and hydrogen peroxide (H2O2)-induced stomatal closure and enhanced ABA-induced H2O2 production. Similar results were observed when silencing SpMPK3 alone, but not when SpMPK1 and SpMPK2 were individually silenced. These data suggest that the functions of SpMPK1 and SpMPK2 are redundant, and they overlap with that of SpMPK3 in drought stress signaling pathways. In addition, we found that SpMPK3 may regulate H2O2 levels by mediating the expression of CAT1. Hence, SpMPK1, SpMPK2, and SpMPK3 may play crucial roles in enhancing tomato plants’ drought tolerance by influencing stomatal activity and H2O2 production via the ABA-H2O2 pathway.
Highlights
The tomato plant, Solanum lycopersicum, is extensively cultivated and consumed around the world and constitutes a major agricultural industry
We found that inhibiting the function of SpMPK1, SpMPK2, and SpMPK3 genes in tomato plants reduced their tolerance to drought
It has been reported that a given MAPKK kinases (MAPKKKs) or MAPKK can activate more than one target kinase, which means that MAPKKKs and MAPKKs function as divergence points in signal transduction [32]
Summary
The tomato plant, Solanum lycopersicum, is extensively cultivated and consumed around the world and constitutes a major agricultural industry. Many signaling pathways are involved in mediating plants’. Mitogen-activated protein kinase (MAPK) cascade, the foundation of signal transduction networks, plays crucial roles in the ability of plants to tolerate and adapt to stresses by regulating stress signal transduction and the expression of relevant genes. The MAPK signaling pathway is a three-tiered phosphorelay cascade consisting of MAPKs (MPKs), which are activated by MAPK kinases (MPKK or MKKs), which in turn are activated by MAPKK kinases (MAPKKKs). An increasing body of evidence suggests, that in plants, MAPK cascades are involved in numerous developmental processes as well as signaling networks associated with stress responses, including tolerance to certain stressors [2,3,4,5,6].
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