MOLECULAR PHYSIOLOGY OF PLANT ABIOTIC STRESS
Arguably as important as inducing responses to a stress is stopping them when they are no longer required. This aspect of stress responses in plant, and signaling in general, has tended to be overlooked. Cellular homeostasis requires that every signaling process involving up- or down- regulation of a given pathway should only be transient, and returning to steady state after a signaling process is as vital to living cells as being able to perceive and transduce changes of their environment. One of the best studied responses of plant cells subjected to water-related stress is the transient increase of the phytohormone abscisic acid (ABA). The increase in active ABA regulates the expression of ABA-responsive genes, some of which are strictly ABA-dependent in that their expression is almost undetectable in absence of elevated levels of cellular ABA. Since the function of these proteins may only be required transiently, a regulatory mechanism for transcriptionally and/or post-translationally regulate their expression should exist. In general during stress, molecular mechanisms aimed at shutting down the ABA-dependent responses, as required at some point for the homeostasis of the plant cell, are poorly understood. The Arabidopsis TSPO (Translocator protein)-related (AtTSPO) is transiently induced by abiotic stresses and ABA treatment.AtTSPO is a membrane protein induced by water-related stresses and ABA treatment in Arabidopsis. Although many stress-induced proteins have been characterized in plants, how plants readjust levels of a stress-induced protein when normal physiological conditions resume has not been addressed. In particular, the questions of how, when, and where the induced proteins are targeted for degradation when their activities become irrelevant await answers. We have shown that ABA-dependent AtTSPO induction is transient, and uncovered exciting insights into the interplay among a stress protein, abscisic acid, tetrapyrrole biosynthesis/scavenging, and autophagy.
Web of a plant cell ER (Endoplasmic Reticulum)
| 4/10/2013 |