Abstract
As global warming progresses, agriculture will likely be impacted enormously by the increasing heat stress (HS). Hence, future crops, especially in the southern Mediterranean regions, need thermotolerance to maintain global food security. In this regard, plant scientists are searching for solutions to tackle the yield-declining impacts of HS on crop plants. Glycine betaine (GB) has received considerable attention due to its multiple roles in imparting plant abiotic stress resistance, including to high temperature. Several studies have reported GB as a key osmoprotectant in mediating several plant responses to HS, including growth, protein modifications, photosynthesis, gene expression, and oxidative defense. GB accumulation in plants under HS differs; therefore, engineering genes for GB accumulation in non-accumulating plants is a key strategy for improving HS tolerance. Exogenous application of GB has shown promise for managing HS in plants, suggesting its involvement in protecting plant cells. Even though overexpressing GB in transgenics or exogenously applying it to plants induces tolerance to HS, this phenomenon needs to be unraveled under natural field conditions to design breeding programs and generate highly thermotolerant crops. This review summarizes the current knowledge on GB involvement in plant thermotolerance and discusses knowledge gaps and future research directions for enhancing thermotolerance in economically important crop plants.
Highlights
Temperature can adversely affect the normal functioning of plant metabolism [1,2]
Glycine betaine (GB) biosynthesis, in higher plants, is a two-step pathway beginning with choline, which is catalyzed by a ferredoxin-dependent Riesketype protein, namely, choline monooxygenase (CMO), and by a soluble NAD+-dependent enzyme [28,29]
GB biosynthesis has different roles in different organelles; for example, chloroplastic GB is actively involved in stress tolerance, while cytosolic GB lacks such functionality
Summary
Temperature can adversely affect the normal functioning of plant metabolism [1,2]. In the last few decades, climate change-induced rising temperatures have beome a major challenge for modern crop production, especially in southern Mediterranean regions [3]. Increasing the capacity of heat stress-induced excessive ROS scavenging is considered an efficient defense strategy for ameliorating heat stress in plants [13]. Plants have naturally adapted various defense mechanisms to counteract harsh environmental conditions such as heat stress These defense mechanisms include an antioxidant machinery, osmolyte accumulation, maintenance of membrane integrity, and increased biosynthesis of heat-shock proteins (HSPs) by upregulating their associated genes’ expression [15,16]. These defense mechanisms are involved in cellular defense against heat stress. We summarize the fundamental impact of GB in inducing heat stress tolerance in economically important crops
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