Evolution of TOR-SnRK dynamics in green plants and its integration with phytohormone signaling networks

Abstract

The Target Of Rapamycin-SNF1-Related Protein Kinase 1 (TOR-SnRK1) arms race is an ancient regulatory mechanism evolved in eukaryotes to regulate nutrient-dependent growth. The autotrophic nature makes plants a distinct class in the eukaryotic lineage. Although TOR-SnRK1 signaling cascade shows highly conserved functions, studies in the past two decades identified many important plant-specific innovations in this pathway. Plants also possess SnRK2 and SnRK3 kinases which are originated from the ancient SnRK1-related kinases and do specialized functions in controlling growth, stress responses and nutrient homeostasis in plants. Recently, an integrative picture has started to emerge where different SnRKs and TOR kinase are highly interconnected to control nutrient and stress responses of plants. Further, these kinases are intimately involved with phytohormone signaling networks which originated at different stages of plant evolution. In this review, we are highlighting the evolution and divergence of TOR-SnRKs signaling components in plants and their communication between each other and phytohormone signaling to fine-tune growth and stress responses in plants.