Shabir H. Wani

Transcription Factors and Plants Response to Drought Stress: Current Understanding and Future Directions

Increasing vulnerability of plants to a variety of stresses such as drought, salt and extreme temperatures poses a global threat to sustained growth and productivity of major crops. Of these stresses, drought represents a considerable threat to plant growth and development. In view of this, developing staple food cultivars with improved drought tolerance emerges as the most sustainable solution toward improving crop productivity in a scenario of climate change. In parallel, unraveling the genetic architecture and the targeted identification of molecular networks using modern “OMICS” analyses, that can underpin drought tolerance mechanisms, is urgently required. Importantly, integrated studies intending to elucidate complex mechanisms can bridge the gap existing in our current knowledge about drought stress tolerance in plants. It is now well established that drought tolerance is regulated by several genes, including transcription factors (TFs) that enable plants to withstand unfavorable conditions, and these remain potential genomic candidates for their wide application in crop breeding. These TFs represent the key molecular switches orchestrating the regulation of plant developmental processes in response to a variety of stresses. The current review aims to offer a deeper understanding of TFs engaged in regulating plant’s response under drought stress and to devise potential strategies to improve plant tolerance against drought.

Transplastomic plants for innovations in agriculture. A review

Food production has to be significantly increased in order to feed the fast growing global population estimated to be 9.1 billion by 2050. The Green Revolution and the development of advanced plant breeding tools have led to a significant increase in agricultural production since the 1960s. However, hundreds of millions of humans are still undernourished, while the area of total arable land is close to its maximum utilization and may even decrease due to climate change, urbanization, and pollution. All these issues necessitate a second Green Revolution, in which biotechnological engineering of economically and nutritionally important traits should be critically and carefully considered. Since the early 1990s, possible applications of plastid transformation in higher plants have been constantly developed. These represent viable alternatives to existing nuclear transgenic technologies, especially due to the better transgene containment of transplastomic plants. Here, we present an overview of plastid engineering techniques and their applications to improve crop quality and productivity under adverse growth conditions. These applications include (1) transplastomic plants producing insecticidal, antibacterial, and antifungal compounds. These plants are therefore resistant to pests and require less pesticides. (2) Transplastomic plants resistant to cold, drought, salt, chemical, and oxidative stress. Some pollution tolerant plants could even be used for phytoremediation. (3) Transplastomic plants having higher productivity as a result of improved photosynthesis. (4) Transplastomic plants with enhanced mineral, micronutrient, and macronutrient contents. We also evaluate field trials, biosafety issues, and public concerns on transplastomic plants. Nevertheless, the transplastomic technology is still unavailable for most staple crops, including cereals. Transplastomic plants have not been commercialized so far, but if this crop limitation were overcome, they could contribute to sustainable development in agriculture.

Transgenic Approaches for Abiotic Stress Tolerance in Crop Plants

Abiotic stresses including drought, salinity and cold are a major challenge for sustainable food production as they may decrease the potential yields in crop plants by 70 %. Success in breeding for better adapted varieties to abiotic stresses depends upon intensive efforts using novel biotechnological approaches, including molecular biology, genetics, plant and cell physiology and breeding. Many abiotic stress-induced genes have been identified and some have been cloned. The use of current molecular biology tools to reveal the control mechanisms of abiotic-stress tolerance, and for engineering stress-tolerant crops is based on the expression of specific stress-related genes. Hence, plant genetic engineering and molecular-marker approaches allow development of abiotic stress-tolerant germplasm. Transgenic plants carrying genes for abiotic stress tolerance are being developed, mainly by using Agrobacterium and biolistic methods; transgenics carrying different genes relating to abiotic stress tolerance have been developed in crop plants like rice, wheat, maize, sugarcane, tobacco, Arabidopsis, groundnut, tomato and potato. This chapter focuses on recent progress in using transgenic technology for the improvement of abiotic-stress tolerance in plants. It includes discussion of metabolic engineering for biosynthesis and accumulation of compatible osmolytes (i.e. proline, glycine betaine, ectoine and polyols), reactive oxygen species formation under abiotic stress, ROS scavenging and detoxification in plant cells, single gene transgenic versus multiple genes and transcription factors and their roles in management of abiotic stresses.

Plant Stress Tolerance: Engineering ABA: A Potent Phytohormone

Abiotic stresses, primarily drought, salinity, heat, cold, flooding and ultra-violet rays are causing widespread crop losses worldwide. Because of the complexity of the stress-tolerance traits, conventional breeding techniques have met with little success in fulfilling the world fooddemands . Therefore, to face the abiotic stresses, novel and potent approaches should be devised and engineering of phytohormones could be a method of choice to increase the crop productivity

Molecular Farming Using Transgenic Approaches

Transgenic plants can be used for molecular farming for the production of recombinant pharmaceutical or industrial compounds. They offer attractive alternatives to produce low-cost recombinant pharmaceuticals or industrially-important proteins on a large scale. The feasibility of precise plant genetic manipulation, high-scale expression of recombinant proteins, rapid and easy scaling up, and convenient storage of raw material and less concern of contamination with human or animal pathogens during downstream processing has attracted biotechnologists to plastid and chloroplast engineering. Crop plants produce large amounts of biomass at low cost and require limited facilities. Molecular farming represents a novel source of molecular medicines, such as plasma proteins, enzymes, growth factors, vaccines and recombinant antibodies, whose medical applications are understood at the molecular level. Edible organs can be consumed as uncooked, unprocessed or partially-processed material, making them ideal for the production of recombinant subunit vaccines, nutraceuticals and antibodies designed for topical application. Based on this prominence, the present chapter is aimed to cover recent advancement for the production of plant pharmaceuticals.

Metabolic Engineering of Compatible Solute Trehalose for Abiotic Stress Tolerance in Plants

It is estimated that by 2050 the world population will reach 9.1 billion, but the production of agricultural products is the same. In order to feed the whole population, global agricultural production should be increased by 60–110 %, and to feed the additional 2.3 billion population, 70 % more food should be grown to fulfill the demand. Due to abiotic stresses, agricultural production is lowered, so now abiotic stresses are a foremost area of concern to fulfill the required food demand. The major abiotic stresses which threaten the food security worldwide are high salinity, drought, submerge tolerance, and cold. To produce stress-tolerant crops, genetic engineering of stress-signaling pathway is one of the main goals of agricultural research. In recent years, biotechnologist is trying to develop a new abiotic stress-tolerant variety by engineering a trehalose metabolism in crops which can have a substantial impact on worldwide food production. Trehalose, a nonreducing disaccharide, has tremendous effects in abiotic stress tolerance and metabolic regulation in a wide range of organisms. Trehalose-6-phosphate synthase (TPS and trehalose-6-phosphate phosphatase (TPP are two key enzymes which help in the biosynthesis of plants. Trehalose is an uncommon sugar present in bacteria, fungi, and desiccation-tolerant higher plants and has exceptional capacities to protect biomolecules by stabilizing dry biological membrane and proteins from environmental stress. It has a multiple function and some of them are species specific. Many research groups showed that there is a linkage between trehalose and abiotic stress by conducting different experiments. They introduced trehalose biosynthetic genes to develop stress tolerance line in important crops like rice, tomato, and potato. Here, in this review, we discuss occurrence, characters, chemical and biological characteristics, uses, pathways, and successful examples in crop plants.

Engineering Phytohormones for Abiotic Stress Tolerance in Crop Plants

Abiotic stresses including salinity, drought, extreme temperatures, and heavy metals are posing serious threats to agricultural yields as well as the quality of produce. This necessitates the production of cultivars capable to withstand the harsh environmental conditions without substantial yield losses. Owing to the complexity underlying stress tolerance traits, conventional breeding techniques have met with limited success and demand effective supplements to feed the growing food demands worldwide. This necessitates the development and deployment of novel and potent approaches, and engineering of phytohormone metabolism could be a method of choice to produce climate resilient crops with higher yields. Phytohormones are considered critical for regulating and coordinating plant growth and development; however, in recent years, they have received great attention for their multifunctional roles in plant responses to environmental stimuli. Creditable research has shown that phytohormones including the classical ones – auxins, cytokinins, ethylene, gibberellins, and newer members including brassinosteroids, jasmonates, and strigolactones – may prove to be potent targets for their metabolic engineering for producing abiotic stress-tolerant crop plants. This chapter presents short description of the roles of phytohormones in abiotic stress responses and tolerance followed by reviewing attempts made by the plant biotechnologists for engineering of phytohormone metabolism, signal, transport, and perception to develop abiotic stress-tolerant crop plants.

Understanding the Phytohormones Biosynthetic Pathways for Developing Engineered Environmental Stress-Tolerant Crops

Plants are significantly subject of diverse environmental stresses. Abiotic stresses are mainly due to nonliving environmental factors such as drought, heat, cold, and salinity, whereas biotic stresses are mainly caused by other living organisms in the surrounding environment such as bacteria, fungi, viruses, nematodes, and insects. A long series of investigations has now developed beyond the doubt that major phytohormones such as auxins, cytokinins (CK), gibberellins (GAs), abscisic acid (ABA), ethylene (ET), brassinosteroids (BRs), salicylic acid (SA), jasmonates (JAs), and strigolactones and their biosynthetic and signaling pathways play central roles in integrating and coordinating the whole plant stress responses. Understanding the mechanisms and the biosynthetic pathways of different phytohormones that can enhance plant stress tolerance could lead to developing an environmental stress-tolerant crop through engineering the target phytohormones biosynthetic pathways. This chapter provides an overview on the relationships between different types of phytohormones and plant response to environmental stresses. We emphasize the significant contribution of transgenerational effects (maternal and epigenetic) on phytohormones biosynthesis. Additionally, the molecular mechanisms and regulation of phytohormones biosynthetic pathways are discussed in details. Omics and metabolic engineering prospective for developing environmental stress-tolerant crops are also highlighted.

Application of Bioinformatics in Understanding of Plant Stress Tolerance

Understanding the complex regulatory pathways of abiotic stress tolerance warrants in-depth study of a biological system. Recent emergence of the novel “-omics” technologies, such as genomics, proteomics, and metabolomics, enables us to study and identify the genetic elements behind systems complexity. The major challenge in this genomics era is to store and handle staggering volume of information contained within the genome scaffolds or even within the transcriptomics data available for more plant species; it would not be an exaggeration to state that the bioinformatics has been efficiently integrated in the modern -omics research. Various bioinformatics softwares and tools like sequence analysis and similarity searching tools; genome sequencing tools; genome annotation tools; de novo genome assembly tools; transcriptome, proteome, and metabolome analysis; and visualization tools help us to analyze biological information providing novel insights into the organization of biological systems. This specific -omics knowledge could subsequently be harnessed to develop improved crop plants in terms of quality and productivity, showing enhanced level of abiotic stress tolerance and disease resistance. The bioinformatics in post-genomics era is revolutionizing the way experiments are designed in molecular biology, thus making substantial contributions in increasing scientific knowledge while adding new functionalities and perspectives to genetic engineering programs for enhancing stress tolerance.

Correction to: In vitro propagation of bamboo species through axillary shoot proliferation: a review

There is an error in one of the last sections of the original publication