Identification of biotic and abiotic stress up-regulated ESTs in Gossypium arboreum

Asiatic desi cotton (Gossypium arboreum) shows great potential against biotic and abiotic stresses. The stress resistant nature makes it a best source for the identification of biotic and abiotic stress resistant genes. As in many plants same set of genes show responding behavior against the various abiotic and biotic stresses. Thus in the present study the ESTs from the G. arboreum drought stressed leaves were subjected to find the up-regulated ESTs in abiotic and biotic stresses through homology and in-silico analysis. A cDNA library has been constructed from the drought stressed G. arboreum plant. 778 clones were randomly picked and sequenced. All these sequences were subjected to in-silico identification of biotic and abiotic up-regulated ESTs. Total 39 abiotic and biotic up-regulated ESTs were identified. The results were further validated by real-time PCR; by randomly selection of ten ESTs. These findings will help to develop stress resistant crop varieties for better yield and growth performance under stresses.     

Structural evolution and function of stress associated proteins in regulating biotic and abiotic stress responses in plants

Adverse environmental conditions greatly influence crop production every year and threaten food security. Plants have a range of signaling networks to combat these stresses, in which several stress-responsive genes and regulatory proteins function together. One such important family of proteins, the Stress Associated Protein (SAP) family, has been identified as a novel regulator of multiple stresses. The SAPs possess a characteristic N-terminal A20 zinc-finger domain combined with either AN1 or C₂H₂ at the C-terminus. SAPs provide tolerance against various abiotic stresses, including cold, salt, drought, heavy metal, and wounding. The majority of SAPs are stress-inducible and have a function in conferring stress tolerance in transgenics. The role of SAPs in regulating biotic stress responses is a newly emerging field among researchers. SAPs interact with many other proteins to execute their functions; however, the detailed mechanism of these interactions needs to be elucidated. In this context, the present review provides a detailed view of the evolution and functions of SAPs in plants. The involvement in crosstalk between abiotic and biotic stress signaling pathways makes SAPs ideal targets to develop crops with tolerance against multiple stresses without any yield penalty. Altogether, we provide current knowledge on SAPs for investigating their role in stress response, which can further be exploited to develop climate-resilient crops through transgene-based, breeding-mediated, or genome-editing approaches.

     

Methylglyoxal detoxification by a DJ-1 family protein provides dual abiotic and biotic stress tolerance in transgenic plants

Methylglyoxal (MG) is a key signaling molecule resulting from glycolysis and other metabolic pathways. During abiotic stress, MG levels accumulate to toxic levels in affected cells. However, MG is routinely detoxified through the action of DJ1/PARK7/Hsp31 proteins that are highly conserved across kingdoms and mutations in such genes are associated with neurodegenerative diseases. Here, we report for the first time that, similar to abiotic stresses, MG levels increase during biotic stresses in plants, likely contributing to enhanced susceptibility to a wide range of stresses. We show that overexpression of yeast Heat shock protein 31 (Hsp31), a DJ-1 homolog with robust MG detoxifying capabilities, confers dual biotic and abiotic stress tolerance in model plant Nicotiana tabacum. Strikingly, overexpression of Hsp31 in tobacco imparts robust stress tolerance against diverse biotic stress inducers such as viruses, bacteria and fungi, in addition to tolerance against a range of abiotic stress inducers. During stress, Hsp31 was targeted to mitochondria and induced expression of key stress-related genes. These results indicate that Hsp31 is a novel attractive tool to engineer plants against both biotic and abiotic stresses.     

Perspective of plant growth promoting rhizobacteria (PGPR) containing ACC deaminase in stress agriculture

Ethylene is a gaseous plant growth hormone produced endogenously by almost all plants. It is also produced in soil through a variety of biotic and abiotic mechanisms, and plays a key role in inducing multifarious physiological changes in plants at molecular level. Apart from being a plant growth regulator, ethylene has also been established as a stress hormone. Under stress conditions like those generated by salinity, drought, waterlogging, heavy metals and pathogenicity, the endogenous production of ethylene is accelerated substantially which adversely affects the root growth and consequently the growth of the plant as a whole. Certain plant growth promoting rhizobacteria (PGPR) contain a vital enzyme, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, which regulates ethylene production by metabolizing ACC (an immediate precursor of ethylene biosynthesis in higher plants) into α-ketobutyrate and ammonia. Inoculation with PGPR containing ACC deaminase activity could be helpful in sustaining plant growth and development under stress conditions by reducing stress-induced ethylene production. Lately, efforts have been made to introduce ACC deaminase genes into plants to regulate ethylene level in the plants for optimum growth, particularly under stressed conditions. In this review, the primary focus is on giving account of all aspects of PGPR containing ACC deaminase regarding alleviation of impact of both biotic and abiotic stresses onto plants and of recent trends in terms of introduction of ACC deaminase genes into plant and microbial species.     

Abiotic and Biotic Stresses and Changes in the Lignin Content and Composition in Plants

Lignin is a polymer of phenylpropanoid compounds formed through a complex biosynthesis route, represented by a metabolic grid for which most of the genes involved have been sequenced in several plants, mainly in the model-plants Arabidopsis thaliana and Populus. Plants are exposed to different stresses, which may change lignin content and composition. In many cases, particularly for plant-microbe interactions, this has been suggested as defence responses of plants to the stress. Thus, understanding how a stressor modulates expression of the genes related with lignin biosynthesis may allow us to develop study-models to increase our knowledge on the metabolic control of lignin deposition in the cell wall. This review focuses on recent literature reporting on the main types of abiotic and biotic stresses that alter the biosynthesis of lignin in plants.