Mulberry MnMAPK1, a group C mitogen-activated protein kinase gene, endowed transgenic Arabidopsis with novel responses to various abiotic stresses

Mitogen-activated protein kinase (MAPK) cascades play key roles in the responses to various biotic and abiotic stresses in plants. Mulberry (Morus L.) is an important economic and ecological perennial tree, which is adaptable to adverse environments, but little is known regarding the molecular mechanisms. In this study, we functionally characterized a group C MAPK gene from Morus, designated as MnMAPK1. A real-time quantitative reverse transcription-PCR analysis demonstrated that the expression of MnMAPK1 could be induced by multiple biotic stresses and exogenous signaling molecules. The MnMAPK1-overexpressed Arabidopsis lines exhibited an enhanced tolerance to salt and H2O2 stresses, but a greater sensitivity to drought and heat stresses. Transcriptomic analysis revealed that MnMAPK1 overexpression widely and largely affected the transcriptome of genes in response to stresses and stimuli. The up-regulation of the genes involved in the reactive oxygen species scavenging-related pathways may contribute to the enhancement of the salt-stress tolerance. Furthermore, the down-regulation of transcripts encoding transcription factors and stress-responsive genes may contribute to the increased sensitivity to drought and heat stresses. Thus, the MnMAPK1 protein may play an important role in plant abiotic-stress tolerance.