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Plants constantly monitor and cope with the fluctuating environment while hosting a diversity of plant-inhabiting microbes. The mode and outcome of plant–microbe interactions, including plant disease epidemics, are dynamically and profoundly influenced by abiotic factors, such as light, temperature, water and nutrients. Plants also utilize associations with beneficial microbes during adaptation to adverse conditions. Elucidation of the molecular bases for the plant–microbe–environment interactions is therefore of fundamental importance in the plant sciences. Following advances into individual stress signaling pathways, recent studies are beginning to reveal molecular intersections between biotic and abiotic stress responses and regulatory principles in combined stress responses. We outline mechanisms underlying environmental modulation of plant immunity and emerging roles for immune regulators in abiotic stress tolerance. Furthermore, we discuss how plants coordinate conflicting demands when exposed to combinations of different stresses, with attention to a possible determinant that links initial stress response to broad-spectrum stress tolerance or prioritization of specific stress tolerance.

Key messageRecent updates in JA biosynthesis, signaling pathways and the crosstalk between JA and others phytohormones in relation with plant responses to different stresses.In plants, the roles of phytohormone jasmonic acid (JA), amino acid conjugate (e.g., JA-Ile) and their derivative emerged in last decades as crucial signaling compounds implicated in stress defense and development in plants. JA has raised a great interest, and the number of researches on JA has increased rapidly highlighting the importance of this phytohormone in plant life. First, JA was considered as a stress hormone implicated in plant response to biotic stress (pathogens and herbivores) which confers resistance to biotrophic and hemibiotrophic pathogens contrarily to salicylic acid (SA) which is implicated in plant response to necrotrophic pathogens. JA is also implicated in plant responses to abiotic stress (such as soil salinity, wounding and UV). Moreover, some researchers have recently revealed that JA controls several physiological processes like root growth, growth of reproductive organs and, finally, plant senescence. JA is also involved in the biosynthesis of various metabolites (e.g., phytoalexins and terpenoids). In plants, JA signaling pathways are well studied in few plants essentially Arabidopsis thaliana, Nicotiana benthamiana, and Oryza sativa L. confirming the crucial role of this hormone in plants. In this review, we highlight the last foundlings about JA biosynthesis, JA signaling pathways and its implication in plant maturation and response to environmental constraints.

Plants being sessile entities are often subjected to varied environmental stresses. They have developed an alternative defense mechanism that involves a vast variety of secondary metabolites to serve as tools to cope up with various stress conditions. The exposure of plant cells to abiotic and biotic stresses initiate multilevel reaction cascades that consequently leads to production and accumulation of various secondary metabolites. Various enzymatic and non-enzymatic molecules comprising the antioxidative defense system comes into play to counteract the undesirable effect of ecological stresses. Energy required as fuel in biosynthesis, transport and storage which comprises the costs for the formation of various transcription factors. When plant experiences stress in combination they express various transcription factors that might help the plant to make flexible signaling cascades to increase plant resistance against one of the stress. Based on this limelight, the present review aims to wrap the influence of different abiotic and biotic factors including salt, drought, heavy metals, UV light, herbivory and pathogenesis on secondary metabolites production and their roles in stress tolerance mechanism in plants.

In field conditions, crops are adversely affected by a wide range of abiotic stresses including drought, cold, salt, and heat, as well as biotic stresses including pests and pathogens. These stresses can have a marked effect on crop yield. The present and future effects of climate change necessitate the improvement of crop stress tolerance. Plants have evolved sophisticated stress response strategies, and genes that encode transcription factors (TFs) that are master regulators of stress-responsive genes are excellent candidates for crop improvement. Related examples in recent studies include TF gene modulation and overexpression approaches in crop species to enhance stress tolerance. However, much remains to be discovered about the diverse plant TFs. Of the >80 TF families, only a few, such as NAC, MYB, WRKY, bZIP, and ERF/DREB, with vital roles in abiotic and biotic stress responses have been intensively studied. Moreover, although significant progress has been made in deciphering the roles of TFs in important cereal crops, fewer TF genes have been elucidated in sorghum. As a model drought-tolerant crop, sorghum research warrants further focus. This review summarizes recent progress on major TF families associated with abiotic and biotic stress tolerance and their potential for crop improvement, particularly in sorghum. Other TF families and non-coding RNAs that regulate gene expression are discussed briefly. Despite the emphasis on sorghum, numerous examples from wheat, rice, maize, and barley are included. Collectively, the aim of this review is to illustrate the potential application of TF genes for stress tolerance improvement and the engineering of resistant crops, with an emphasis on sorghum.

Compelling evidence indicates that free polyamines (PAs) (mainly putrescine, spermidine, spermine, and its isomer thermospermine), some PA conjugates to hydroxycinnamic acids, and the products of PA oxidation (hydrogen peroxide and γ-aminobutyric acid) are required for different processes in plant development and participate in abiotic and biotic stress responses. A tight regulation of PA homeostasis is required, since depletion or over-accumulation of PAs can be detrimental for cell viability in many organisms. In plants, homeostasis is achieved by modulation of PA biosynthesis, conjugation, catabolism, and transport. However, recent data indicate that such mechanisms are not mere modulators of PA pools but actively participate in PA functions. Examples are found in the spermidine-dependent eiF5A hypusination required for cell division, PA hydroxycinnamic acid conjugates required for pollen development, and the involvement of thermospermine in cell specification. Recent advances also point to implications of PA transport in stress tolerance, PA-dependent transcriptional and translational modulation of genes and transcripts, and posttranslational modifications of proteins. Overall, the molecular mechanisms identified suggest that PAs are intricately coordinated and/or mediate different stress and developmental pathways during the lifespan of plants.

Enhancing rice yield in upland rice systems through genetic improvement remains a major challenge in the tropics. This review aims to provide the trends on upland rice cultivation over the last 30 years and recent distribution of upland rice in the tropics, and to report progress in studies on genetic improvement for enhancing productivity in Africa, Asia, and Latin America. While upland rice cultivation area has reduced in Asia and Latin America over the last 30 years, the area in Africa has increased. The current share of upland rice area in total rice area is related to rainfall and gross national income per capita, especially in Africa, and higher share is associated with lower rice self-sufficiency at national level. Breeding programs in Asia and Latin America have developed high-yielding varieties using indica materials as parents. In Africa, New Rice for Africa (NERICA) varieties were developed from crosses between improved tropical japonica and Oryza glaberrima. However, recent studies report that there is scope for improving existing NERICA using upland indica materials from Asia. In highlands of Africa, there are ongoing breeding programs using japonica varieties, such as the Nepalese Chhomrong Dhan. Key important plant traits used in the breeding programs are not largely different across regions, especially intermediate plant height and tillering capacity (which may be related to weed-suppressive ability), and high harvest index. In conclusion, we propose an international network for breeding upland rice with accelerating seed exchange across regions that could enhance upland rice productivity through genetic improvement.

Plants interact with diverse microbial communities and share complex relationships with each other. The intimate association between microbes and their host mutually benefit each other and provide stability against various biotic and abiotic stresses to plants. Endophytes are heterogeneous groups of microbes that live inside the host tissue without showing any apparent sign of infection. However, their functional attributes such as nutrient acquisition, phytohormone modulation, synthesis of bioactive compounds, and antioxidant enzymes of endophytes are similar to the other rhizospheric microorganisms. Nevertheless, their higher colonization efficacy and stability against abiotic stress make them superior to other microorganisms. In recent studies, the potential role of endophytes in bioprospecting has been broadly reported. However, the molecular aspect of host–endophyte interactions is still unclear. In this study, we have briefly discussed the endophyte biology, colonization efficacy and diversity pattern of endophytes. In addition, it also summarizes the molecular aspect of plant–endophyte interaction in biotic stress management.

Phospholipase C (PLC) generates various second messenger molecules and mediates phospholipid hydrolysis. In recent years, the important roles of plant and fungal PLC in disease resistance and pathogenicity, respectively, have been determined. However, the roles of PLC in plants and fungi are unintegrated and relevant literature is disorganized. This makes it difficult for researchers to implement PLC‐based strategies to improve disease resistance in plants. In this comprehensive review, we summarize the structure, classification, and phylogeny of the PLCs involved in plant biotic stress resistance and fungal pathogenicity. PLCs can be divided into two groups, nonspecific PLC (NPC) and phosphatidylinositol‐specific PLC (PI‐PLC), which present marked differences in phylogenetic evolution. The products of PLC genes in fungi play significant roles in physiological activity and pathogenesis, whereas those encoded by plant PLC genes mediate the immune response to fungi. This review provides a perspective for the future control of plant fungal diseases. This review provides a summary on the classification, structure, evolution, and molecular function of phospholipase C (PLC) in plants and fungi, exploring the potential mechanism of PLC in disease resistance and fungal pathogenicity.

Reliable large-scale maize production is an essential component of global food security; however, sustained efforts are needed to ensure optimized resilience under diverse crop stress conditions. Climate changes are expected to increase the frequency and intensity of both abiotic and biotic stress. Protective phytochemicals play an important role in both abiotic stress resilience and resistance to biotic challenges, yet the concentration and composition of these phytochemicals are also dependent on climate variables. We review the research on the effects of climate change associated abiotic stresses on three classes of maize defense metabolites, including benzoxazinoids, volatile organic compounds, and terpenoid phytoalexins. Despite significant knowledge gaps that still exist, it is evident that climate change will influence maize phytochemicals associated with resilient productivity. While broad generalizations are not yet possible, climate induced changes in phytochemicals are context specific and dependent upon developmental stage and tissue type. Under conditions of drought, maize modulates different classes of defense phytochemicals to protect the above-and belowground tissues. Aboveground the benzoxazinoid defenses are stimulated, but belowground terpenoid phytoalexins are predominantly deployed. Changes in the allocation or distribution of the different classes of defense metabolites or signaling molecules have the potential to further shape the biodiversity and abundance of pests within the maize agroecosystem. A better understanding of the underlying genetics, biosynthetic pathways, regulation and precise biological roles of maize phytochemicals modulated by arrays of climatic conditions will be required to ensure optimal plant resilience and productivity in the face of combined biotic and abiotic stresses.

Global climate change has drastically affected natural ecosystems and crop productivity. Among several factors of global climate change, CO2 is considered to be the dynamic parameter that will regulate the responses of all biological system on earth in the coming decade. A number of experimental studies in the past have demonstrated the positive effects of elevated CO2 on photosynthesis, growth and biomass, biochemical and physiological processes such as increased C:N ratio, secondary metabolite production, as well as phytohormone concentrations. On the other hand, elevated CO2 imparts an adverse effect on the nutritional quality of crop plants and seed quality. Investigations have also revealed effects of elevated CO2 both at cellular and molecular level altering expression of various genes involved in various metabolic processes and stress signaling pathways. Elevated CO2 is known to have mitigating effect on plants in presence of abiotic stresses such as drought, salinity, temperature etc., while contrasting effects in the presence of different biotic agents i.e. phytopathogens, insects and herbivores. However, a well-defined crosstalk is incited by elevated CO2 both under abiotic and biotic stresses in terms of phytohormones concentration and secondary metabolites production. With this background, the present review attempts to shed light on the major effects of elevated CO2 on plant growth, physiological and molecular responses and will highlight the interactive effects of elevated CO2 with other abiotic and biotic factors. The article will also provide deep insights into the phytohormones modulation under elevated CO2.