Physiological, biochemical, and molecular mechanisms of heat stress tolerance in plants

Abstract

High temperature (HT) stress is a major environmental stress that limits plant growth, metabolism, and productivity worldwide. Plant growth and development involve numerous biochemical reactions that are sensitive to temperature. Plant responses to HT vary with the degree and duration of HT and the plant type. HT is now a major concern for crop production and approaches for sustaining high yields of crop plants under HT stress are important agricultural goals. Plants possess a number of adaptive, avoidance, or acclimation mechanisms to cope with HT situations. In addition, major tolerance mechanisms that employ ion transporters, proteins, osmoprotectants, antioxidants, and other factors involved in signaling cascades and transcriptional control are activated to offset stress-induced biochemical and physiological alterations. Plant survival under HT stress depends on the ability to perceive the HT stimulus, generate and transmit the signal, and initiate appropriate physiological and biochemical changes. HT-induced gene expression and metabolite synthesis also substantially improve tolerance. The physiological and biochemical responses to heat stress are active research areas, and the molecular approaches are being adopted for developing HT tolerance in plants. This article reviews the recent findings on responses, adaptation, and tolerance to HT at the cellular, organellar, and whole plant levels and describes various approaches being taken to enhance thermotolerance in plants.

Figure 1

Major effects of high temperature on plants.

Figure 2

Sites of production of reactive oxygen species in plants [5].

Figure 3

Classification of plants on the basis of their heat tolerance.

Figure 4

Different adaptation mechanisms of plants to high temperature. A: Avoidance, T: Tolerance.

Figure 5

Schematic illustration of heat induced signal transduction mechanism and development of heat tolerance in plants.

Figure 6

Schematic diagram showing the molecular regulatory mechanism of heat shock proteins based on a hypothetical cellular model. Upon heat stress perceived by the plant cell, (a) monomeric heat shock factors (HSFs) are entering into the nucleus; (b) from the cytoplasm. In the nucleus, HSF monomers are form active trimer; (c) that will bind; (d) to the specific genomic region (promoter or heat shock element, HSE) of the respective heat shock gene (HSG). Molecular dissection of the HSF binding region of HSE showing that it is consists of one DNA binding domain and two domains for trimerization of HSFs. Successful transcription (e) translation and post-translational modification; (f) lead to produce functional HSP to protect the plant cell and responsible for heat stress tolerance.

Figure 7

Diagram representing integrated circuit of different “omics” approaches that are connected to each other at molecular genetic level associated with heat stress tolerance in plants.