Abstract
Global development has generated a plethora of unfavorable and adverse environmental factors for the living organisms in the ecosystem. Plants are sessile organisms, and they are crucial to sustain life on earth. Since plants are sessile, they face a great number of environmental challenges related to abiotic stresses, such as temperature fluctuation, drought, salinity, flood and metal contamination. Salinity and drought are considered major abiotic stresses that negatively affect the plants’ growth and production of useful content. However, plants have evolved various molecular mechanisms to increase their tolerance to these environmental stresses. There is a whole complex system of communication (cross-talk) through massive signaling cascades that are activated and modulated in response to salinity and drought. Secondary metabolites are believed to play significant roles in the plant’s response and resistance to salinity and drought stress. Until recently, attempts to unravel the biosynthetic pathways were limited mainly due to the inadequate plant genomics resources. However, recent advancements in generating high-throughput “omics” datasets, computational tools and functional genomics approach integration have aided in the elucidation of biosynthetic pathways of many plant bioactive metabolites. This review gathers comprehensive knowledge of plants’ complex system that is involved in the response and resistance to salinity and water deficit stresses as abiotic stress. Additionally, it offers clues in determining the genes involved in this complex and measures its activity. It covers basic information regarding the signaling molecules involved in salinity and drought resistance and how plant hormones regulate the cross-talking mechanism with emphasis on transcriptional activity. Moreover, it discusses many studies that illustrate the relationship between salinity and drought and secondary metabolite production. Furthermore, several transcriptome analysis research papers of medicinal plants are illustrated. The aim of this review is to be a key for any researcher that is aspiring to study the relationship between salinity and drought stresses and secondary metabolite production at the transcriptome and transcription level.
Highlights
Due to the plants’ sessility and inability to migrate in nature, they are more prone to being affected by a great number of abiotic stresses such as salinity, drought, heat and radiation
Theplant plant response response to to abiotic abiotic stresses stresses can canbe bedescribed describedas asthe thecoordination coordinationof ofexpression expressionof ofgenes genesthat thatencode encodefor foraa variety variety of of products to the theplant’s plant’sadaptation adaptationtotoabiotic abiotic stresses. Those prodproducts that that contribute to stresses. Those products ucts could carry out any function supports the plant in adaptation the adaptation tostress; the stress; could carry out any function that that supports the plant in the to the they they could be,instance, for instance, secondary metabolites carry essential protective funccould be, for secondary metabolites thatthat carry out out essential protective functions against abiotic stresses, transcription factors that that facilitate the activation of second-level tions against abiotic stresses, transcription factors facilitate the activation of secondstress-inducible genesgenes or any functional or regulatory molecules level stress-inducible or other any other functional or regulatory molecules
In order to fight the harmful effect of stress, the plant manages a number of regulatory events involving secondary messengers, signaling proteins, hormones and a variety of stress-inducible transcription factors and their putative target downstream genes
Summary
Due to the plants’ sessility and inability to migrate in nature, they are more prone to being affected by a great number of abiotic stresses such as salinity, drought, heat and radiation Those abiotic stresses are considered major challenges for the development and growth of the plants and potentially influence the yield and quality of the useful products that provide medicinal or nutritional benefits to humans [1]. Stress-related molecules such as abscisic acid (ABA), jasmonic acid (JA) [7], ROS, calcium ions, a variety of transcription factors (TFs) and other regulatory and functional proteins all interact together in a spectacular manner in order to perform a remarkable adaptation to the abiotic stresses [8,9] This communication between secondary messengers, phytohormones, DNA-binding proteins and stress-inducible genes is known as “cross-talk” [9,10]. This review focuses on how these regulatory events impact the secondary metabolite production in some important plant pharmaceuticals
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