Plant organ senescence – regulation by manifold pathways

Abstract

Senescence is the final stage of plant ontogeny before death. Senescence may occur naturally because of age or may be induced by various endogenous and exogenous factors. Despite its destructive character, senescence is a precisely controlled process that follows a well-defined order. It is often inseparable from programmed cell death (PCD), and a correlation between these processes has been confirmed during the senescence of leaves and petals. Despite suggestions that senescence and PCD are two separate processes, with PCD occurring after senescence, cell death responsible for senescence is accompanied by numerous changes at the cytological, physiological and molecular levels, similar to other types of PCD. Independent of the plant organ analysed, these changes are focused on initiating the processes of cellular structural degradation via fluctuations in phytohormone levels and the activation of specific genes. Cellular structural degradation is genetically programmed and dependent on autophagy. Phytohormones/plant regulators are heavily involved in regulating the senescence of plant organs and can either promote [ethylene, abscisic acid (ABA), jasmonic acid (JA), and polyamines (PAs)] or inhibit [cytokinins (CKs)] this process. Auxins and carbohydrates have been assigned a dual role in the regulation of senescence, and can both inhibit and stimulate the senescence process. In this review, we introduce the basic pathways that regulate senescence in plants and identify mechanisms involved in controlling senescence in ephemeral plant organs. Moreover, we demonstrate a universal nature of this process in different plant organs; despite this process occurring in organs that have completely different functions, it is very similar. Progress in this area is providing opportunities to revisit how, when and which way senescence is coordinated or decoupled by plant regulators in different organs and will provide a powerful tool for plant physiology research.

Endogenous ascorbic acid delays ethylene-induced leaf senescence in Arabidopsis thaliana

“…AsA alleviated the damage of ROS: ROS are unavoidable byproducts of cellular metabolism (Xu et al 2017). Plants produce more ROS during aging process (Wojciechowska et al 2018). If the balance of ROS generation and scavenging is destroyed, excess ROS would attack cell components, such as chloroplasts and cell membrane.…”

“…We compared the expression levels of SAGs, which are believed to be useful molecular markers for leaf senescence, among the three lines during ET-induced aging process (Hensel et al 1993, Wojciechowska et al 2018. The results showed that the expression of SAG2, SAG12, SAG13, SAG20, SAG21 were all at low level and there were no significant differences between them before ethephon spraying.…”

РЕГУЛЯЦИЯ ОТТОКА АССИМИЛЯТОВ В ЗЕРНОВКИ ДЛЯ ПОВЫШЕНИЯ ПРОДУКТИВНОСТИ ПОСЕВОВ РИСА (Oryza sativa L.) ПРИ ВЫРАЩИВАНИИ У СЕВЕРНОЙ ГРАНИЦЫ АРЕАЛА КУЛЬТУРЫ

“…senium -старение). Сеникация посевов зерновых культур приводит к медленному отмиранию листьев, сходному с естественным старением (15). Механизм действия сениканта заключается в ускорении обмена веществ в тканях растений и повышении скорости оттока пластических веществ из листьев и стеблей в метелку (колос).…”

Abscisic Acid and Jasmonate Metabolisms Are Jointly Regulated During Senescence in Roots and Leaves of Populus trichocarpa

“…In crops, this process usually overlaps with the reproductive phase and might influence reducing crop yield when it is induced prematurely or/and under unfavorable environmental conditions [2]. The onset of senescence may be related to age [3,4] or can be stimulated by internal factors, such as reactive oxygen species (ROS) or changes in phytohormone level, as well as external factors such as photoperiod, temperature, nutrient deficiency, or shading [5][6][7][8]. While the process of senescence appears to be outwardly destructive, the fact that it is a highly regulated process allows plants to relocate a significant portion of valuable nutrients from senescing organs to other tissues so that they can be re-utilized rather than lost [9,10].…”

“…One of the most characteristic features of senescence is an increase of catabolic metabolic reactions in relation to anabolic ones [11]. This shift leads to the degradation of individual organelles and eventually the rupture of the tonoplast, protoplast acidification, and cell death [8,[12][13][14]. Chloroplasts, which contain approximately 80% of total leaf nitrogen, are one of the first organelles to be degraded [15,16].…”