Using Transcriptome to Discover a Novel Melatonin-Induced Sodic Alkaline Stress Resistant Pathway in Solanum lycopersicum L.

Melatonin plays important roles in multiple stress responses. However, the downstream signaling pathway and molecular mechanism are unclear until now. Here, we not only revealed the transcriptional control of melatonin-induced sodic alkaline stress tolerance, but also described a screen for key downstream transcriptional factors of melatonin through transcriptome analysis. The melatonin-induced transcriptional network of hormone, transcriptional factors and functional genes has been established under both control and stress conditions. Among these, six candidates of transcriptional factors have been identified via Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis. Using the virus-induced gene silencing approach, we confirmed that DREB1 alpha and IAA3 were key downstream transcriptional factors of melatonin-induced sodic alkaline stress tolerance at the genetic level. The transcriptions of DREB1 alpha and IAA3 could be activated by melatonin or sodic alkaline treatment. Interestingly, we found that DREB1 alpha could directly upregulate the expression of IAA3 by binding to its promoters. Moreover, several physiological processes of Na+ detoxification, dehydration resistance, high pH buffering and reactive oxygen species scavenging were confirmed to depend or partly depend on DREB1 alpha and IAA3 pathway in melatonin-induced stress tolerance. Taken together, this study suggested that DREB1 alpha and IAA3 are positive resistant modulators, and provided a direct link among melatonin, DREB1 alpha and IAA3 in the sodic alkaline stress tolerance activating in tomato plants.