Brassinosteroid action and its relation with heat stress mechanisms in plants

Abstract

Brassinosteroids (BRs) are plant steroid hormones which can regulate several physiological effects in plants, including promotion of cell growth and induction of heat stress tolerance. BR-biosynthesis and signaling mutants show a striking dwarf phenotype and these mutants may therefore lead to intrinsic cellular stress. However, how stress mechanisms could function during BR action is poorly understood. This review will focus on stress gene/protein and metabolites that have showed to be altered during BR-induced heat tolerance and as a result of changed BR content and perception. Recent studies on proteomics and microarray of BR-treated tissues or BR-related mutants have revealed up/down regulation of specific enzymes/genes related to reactive oxygen scavenging, redox control, protein folding, and others. We will specifically discuss potential roles for Heat Shock Proteins, Antioxidant metabolites and enzymes in BRinduced thermal tolerance. In addition, as stress mechanisms are not exclusive of plants under stressful situations, the review will also discuss on how these protective factors may be implicated in classical BR effects during normal growth stimulation. Putative models to explain the role of Antioxidants, Oxidants and Heat Shock Proteins in BR action will be presented.