Enigmas of senescence: a reappraisal on the hormonal crosstalk and the molecular mechanisms

Abstract

Due to the already strained and severely challenged agricultural ecosystems of the modern world, predicted changes in life cycle of plants, including leaf senescence are receiving significant attention from stakeholders. The onset, progression and terminal phases of leaf senescence are greatly influenced by plant hormones. The senescence of leaves is accelerated by ethylene, jasmonic acid (JA), salicylic acid (SA), abscisic acid (ABA), brassinosteroids and strigolactones (SLs), whereas it is postponed by cytokinins (CKs), gibberellic acid (GA) and auxins. The crosstalk and signal transduction pathways between these growth regulators have been found to regulate leaf senescence by orchestrating various developmental and environmental factors. Premature leaf senescence lessens the plant’s nutritional capacity and shortens the vegetative production schedule, prompting an early transition from the vegetative to the reproductive stage and diminishing crop potential. As a result, a complete understanding of leaf senescence and finding novel ways to delay it is crucial for agricultural productivity. The ability to manipulate leaf senescence for agricultural enhancement has been made possible by significant advances in physiological and molecular awareness of leaf senescence. Although studies pertaining to leaf senescence have been given steadily more attention, there are still numerous challenges that need to be resolved. In this perspective, this review focuses on current advances in understanding the leaf senescence by molecular and genetic analyses with an emphasis on hormonal regulation of leaf senescence. We also hypothesize future research to better comprehend leaf senescence by employing various current technologies.