Heat Stress Tolerance in Plants: Physiological, Molecular and Genetic Perspectives
A world population is 7.3 billion and by 2050 it is expected to reach 9.7 billion while as at the same time agricultural productivity is poorly exaggerated due to the mounting environmental constraints as a result of climate change. One of prevalent environmental stress encountered by plants during their important growth stages is the heat stress. Heat stress is defined as a period in which temperatures are hot enough for a sufficient period of time to cause irreversible damage to plant function or development. Exposure to heat stress for prolonged periods can even result in plant death. Plants can be damaged by either high day or high night temperatures and by either high air or soil temperatures. Predictions indicate that temperatures will intensify by another 2-6°C by the climax of this century and likelihood to induce heat stress more frequently and severely, begetting to serious reduction of crops yield. The genetic basis of heat adaptation is poorly understood. Conventional breeding methods have met with limited success in improving the heat stress tolerance of important crop plants through inter-specific or inter-generic hybridization. Therefore, it is imperative to accelerate the efforts for unravelling the biochemical, physiological and molecular mechanisms underlying heat stress tolerance in plants.
Heat stress can induce diverse physiological and molecular responses in plants that lead to various cellular metabolic processes disturbance, impair membrane stability, cause protein denaturation and thermal aggregation and consequently affect plant growth and development. The heat stress response is also illustrated by inhibition of regular transcription and translation, elevated expression of heat shock proteins (HSPs) and induction of heat tolerance. During extreme heat stress conditions, signaling pathways leading to apoptotic cell death are also activated. As molecular chaperones, HSPs offer protection to cells against the destructive effects of heat stress and augment survival. The improved expression of HSPs is regulated by heat shock transcription factors (HSFs). Recent advances in molecular genetic approaches have provided new insights into the plant heat stress response. The QTL-based approaches allow loci to be identified markers that are linked to heat tolerance. Further, discoveries of novel genes and pathways, analyses of expression patterns and the determination of function of these genes during heat stress adaptation will offer the base for efficient engineering strategies with the aim to enhance heat stress tolerance in plants. Recent studies involving full genome profiling/sequencing, mutational and transgenic plant analyses have provided a deep insight of the complex transcriptional mechanism that operates under heat stress. Through this book, we intend to integrate the contributions from potential plant scientists targeting heat stress tolerance mechanisms using physiological, biochemical, molecular, and genetic approaches.