Advances in Plant Tolerance to Abiotic Stresses

Abstract

During the last 50 years, it has been shown that abiotic stresses influence plant growth and crop production greatly, and crop yields have evidently stagnated or decreased in economically important crops, where only high inputs assure high yields. The recent manifesting effects of climate change are considered to have aggravated the negative effects of abiotic stresses on plant productivity. On the other hand, the complexity of plant mechanisms controlling important traits and the limited availability of germplasm for tolerance to certain stresses have restricted genetic advances in major crops for increased yields or for improved other traits. However, some level of success has been achieved in understanding crop tolerance to abiotic stresses; for instance, identification of abscisic acid (ABA) receptors (e.g., ABA-responsive element (ABRE) binding protein/ABRE binding factor (AREB/ABF) transcription factors), and other regulons (e.g., WRKYs, MYB/ MYCs, NACs, HSFs, bZIPs and nuclear factor-Y (NF-Y)), has shown potential promise to improve plant tolerance to abiotic stresses. Apart from these major regulons, studies on the post-transcriptional regulation of stress-responsive genes have provided additional opportunities for addressing the molecular basis of cellular stress responses in plants. This chapter focuses on the progress in the study of plant tolerance to abiotic stresses, and describes the major tolerance pathways and implicated signaling factors that have been identified, so far. To link basic and applied research, genes and proteins that play functional roles in mitigating abiotic stress damage are summarized and discussed.In the past 100 years, conventional breeding ( Figure 2; based on observed variation and controlled mating) approaches have randomly exploited these plant tolerance mechanisms with limited success. Moreover, in vitro induced variations have also shown little progress in the improvement of plants against abiotic stresses. These conventional breeding approaches are limited by the complexity of stress tolerance traits coupled with less genetic Plant Genomics 168 variation exhibited by most crops due to domestication bottlenecks. The recent reports that the cultivated gene pool of major cereal crops, e.g., rice, maize and wheat, has reduced in genetic variation compared to wild relatives [10-12], raises concern, and could probably undermine the current efforts to identify genetic sources of resistance within the cultivated genepools. It is important, therefore, to consider exploring alternative sources of resistance by incorporating modern techniques into traditional breeding strategies to develop stresstolerant crops (Figure 2).Recently, with the support of genomics, targeted genetic studies involving QTL mapping and validation, identification of key regulatory genes, e.g., genes encoding for ABA receptors, developments in transcriptional and post-transcriptional regulation of stress-responsive genes and studies on hormonal interactions during plant response to stress, have provided opp...

Elicitor and Receptor Molecules: Orchestrators of Plant Defense and Immunity

“…Ve1 is an example of a plant receptor molecule in tomato, which binds to the Ave1 elicitor molecule from fungi. Ve1 can also be introduced as the PRR or R protein where the Ave1 peptide is referred to as the effector acting as MAMP [41][42][43].…”

“…General elicitors are involved in the general resistance signaling pathways, while race-specific elicitors are associated with R gene-mediated signaling [101]. Elicitors that are capable of triggering defense in both non-host and host plants through the perceived presence of potential pathogens are known as general elicitors [41,[102][103][104][105][106]. Most general elicitors are essentially present in pathogen cell walls as structural components e.g., glucan, chitin, flagellin, and lipopolysaccharides (LPS).…”

Abiotic Stress Responses and Microbe-Mediated Mitigation in Plants: The Omics Strategies

“…Their interactions with the plants evoke various kinds of local and systemic responses that improve metabolic capability of the plants to fight against abiotic stresses ( Nguyen et al, 2016 ). A testament to the important attributes of the microbial interactions with plants is significant number of accumulating pieces of evidence that suggest in-depth mechanisms based on plant–microbe interactions that offer modulation of cellular, biochemical and molecular mechanisms connected with stress tolerance ( Bakker et al, 2012 ; Onaga and Wydra, 2016 ). Growing interest in uncultured microbes, especially from the rhizosphere of the crop plants, depleted and degraded soils, soils with disturbed fertility status and endophytic communities that potentially represent ‘obligate endophytes’ inhabiting plant tissues deciphered multi-phasic functions associated with the stress tolerance in microbial communities.…”

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“…[30] Several studies reported the imperative characteristics of the microbial communications with plants that propose mechanisms based on plant-microorganism associations that accentuated the biochemical, molecular, and cellular mechanisms of plant defense against stresses. [31,32] Studies on plant microbiome at molecular, physiological, and biochemical levels observed that plant-microbes associations communicate plant responses against stress conditions. [33] Technological developments also facilitated understanding of gene editing systems, RNAi-mediated gene silencing, mutant technology, proteomic analysis, and metabolite profiling to reveal voluminous molecular information that helped in improving our understanding of microbe-interactions.…”