ABA and MAPK signaling-mediated transcriptional regulation of drought and salinity responses in grasses

The adverse effects of drought and salinity stress are associated with various stress-signaling pathways and transcription factors, which can be unique or shared by both salt and drought stresses. This article provides an overview of recent advances in grasses, focusing on hormonal signaling, the mitogen-activated protein kinase (MAPK) cascade, stress signal transduction molecules (calcium, reactive oxygen species [ROS], γ-aminobutyric acid [GABA]), and transcriptional and post-transcriptional regulation under drought and salt stress. Studies suggest that signaling molecules can overlap between salt and drought stress; therefore, studying the subsequent signal transduction pathways is of great importance. Transcriptomic studies highlight stress-specific gene regulation in hormone signaling (e.g., ion transporters are strongly upregulated under salt stress, whereas abscisic acid [ABA]-related genes, the growth-promoting hormones, including indoleacetic acid [IAA] and gibberellic acid [GA], are downregulated under drought). ABA signaling, MAPK cascade, ROS pathway, and calcium signaling are central to both stresses. However, salt stress mostly involves ABA signaling, rapid MAPK activation, and ion homeostasis. Studies highlighted genotype-specific responses and tissue-specific regulation of hormone signal transduction and MAPK signaling. The integration of these pathways underscores the significance of molecular crosstalk in drought and salinity adaptation, offering opportunities for genetic engineering and breeding programs to enhance stress tolerance in grass species.