Phytohormones Trigger Drought Tolerance in Crop Plants: Outlook and Future Perspectives

In the past and present, human activities have been involved in triggering global warming, causing drought stresses that affect animals and plants. Plants are more defenseless against drought stress; and therefore, plant development and productive output are decreased. To decrease the effect of drought stress on plants, it is crucial to establish a plant feedback mechanism of resistance to drought. The drought reflex mechanisms include the physical stature physiology and biochemical, cellular, and molecular-based processes. Briefly, improving the root system, leaf structure, osmotic-balance, comparative water contents and stomatal adjustment are considered as most prominent features against drought resistance in crop plants. In addition, the signal transduction pathway and reactive clearance of oxygen are crucial mechanisms for coping with drought stress via calcium and phytohormones such as abscisic acid, salicylic acid, jasmonic acid, auxin, gibberellin, ethylene, brassinosteroids and peptide molecules. Furthermore, microorganisms, such as fungal and bacterial organisms, play a vital role in increasing resistance against drought stress in plants. The number of characteristic loci, transgenic methods and the application of exogenous substances [nitric oxide, (C28H48O6) 24-epibrassinolide, proline, and glycine betaine] are also equally important for enhancing the drought resistance of plants. In a nutshell, the current review will mainly focus on the role of phytohormones and related mechanisms involved in drought tolerance in various crop plants.

Melatonin Promotes SGT1-Involved Signals to Ameliorate Drought Stress Adaption in Rice

Drought has become one of the environmental threats to agriculture and food security. Applications of melatonin (MT) serve as an effective way to alleviate drought stress, but the underlying mechanism remains poorly understood. Here, we found that foliar spray of 100-µM MT greatly mitigated the severe drought stress-induced damages in rice seedlings, including improved survival rates, enhanced antioxidant system, and adjusted osmotic balance. However, mutation of the suppressor of the G2 allele of skp1 (OsSGT1) and ABSCISIC ACID INSENSITIVE 5 (OsABI5) abolished the effects of MT. Furthermore, the upregulated expression of OsABI5 was detected in wild type (WT) under drought stress, irrespective of MT treatment, whereas OsABI5 was significantly downregulated in sgt1 and sgt1abi5 mutants. In contrast, no change of the OsSGT1 expression level was detected in abi5. Moreover, mutation of OsSGT1 and OsABI5 significantly suppressed the expression of genes associated with the antioxidant system. These results suggested that the functions of OsSGT1 in the MT-mediated alleviation of drought stress were associated with the ABI5-mediated signals. Collectively, we demonstrated that OsSGT1 was involved in the drought response of rice and that melatonin promoted SGT1-involved signals to ameliorate drought stress adaption.

Overexpression of Rice Gene Lsi1 (Low Silicon Gene 1) Enhances The Plant-Microbe Interaction Resulting In Improved Chilling Tolerance

Chilling is an environmental phenomenon that hampers the plant growth. Related studies are mainly on based on the aerial plant parts. While, below ground to rhizosphere microbiome have been neglected under low temperature stress. The overexpression of Lsi1 in Dular significantly enhances its proline concentration compared with wild type Dular. This overexpression phenomenon maintains the osmotic balance of cells through influx of Ca2+, K+, H+ and efflux of Na+. The calcium deposition and the activity of plasma membrane H+-ATPase determined in root tip was consistent with the obtained ion flux results. In addition, the high-throughput sequencing results showed significant variation among identified 84 genera in different rhizocompartments (rhizosphere, rhizoplane and endosphere). The identified bacteria were associated with photosynthesis, energy metabolism, nitrogen fixation and defense, which were significantly increased in overexpressed plant. While, the number of pathogenic microorganisms associating were significantly reduced. Our findings suggests that the stability of ion balance in overexpressed plant roots affects the structure of microbial community in soil. To conclude, the over expression of Lsi1 gene enhanced cold tolerance of rice and its underlying mechanisms were comprehensively analyzed which can further impart its role in the stress tolerant rice plants.

EXTRACORPOREAL DETOXIFICATION METHODS IN THE PATHOGENETIC THERAPY OF OBSTETRIC SEPSIS

Раннее включение НВВГФ в комплексном лечении сепсиса и септического шока приводит к снижению клинических признаков эндотоксикоза, стабилизации гемодинамики в более ранние сроки, что связано с быстрой элиминацией цитокинов, коррекцией осмотического равновесия, увеличением диуреза, благодаря более раннему протезированию гомеостатической функции почек. Early inclusion of NVHF in the complex treatment of sepsis and septic shock leads to a decrease in clinical signs of endotoxicosis, stabilization of hemodynamics at an earlier time, which is associated with rapid elimination of cytokines, correction of osmotic balance, increased urine output due to earlier prosthetics of homeostatic renal function.

MECHANISM OF SALT TOLERANCE IN Vitex trifolia linn. var. simplicifolia Cham: ION HOMEOSTASIS, OSMOTIC BALANCE, ANTIOXIDANT CAPACITY AND PHOTOSYNTHESIS

Vitex trifolia Linn. var. simplicifolia Cham is a medicinal aromatic plant and perennial halophyte growing in the coastal areas around the Bohai Sea in China. The aim of this study was to investigate the salt tolerance mechanisms of V. trifolia when subjected to different concentrations of NaCl (0, 90, 180, 270, 360 and 450 mM) by measuring growth parameters, ion contents, proline, soluble sugar, soluble protein, malondialdehyde (MDA), photosynthetic pigment contents, chlorophyll fluorescence parameters and antioxidant enzyme activities. The plants died when the NaCl concentration reached 450 mM 20 days after salt stress. Biomass and shoot growth were inhibited by increasing salinity, while root growth was promoted at a NaCl concentration ranging from 90 to 270 mM. Na+ and Cl– accumulation was markedly promoted in both leaves and roots with increasing salinity, while no significant changes were observed in the K+ concentration and K+/Na+ ratio in the leaves. Proline, soluble sugar and soluble protein contents increased significantly with increasing salinity. In order to eliminate the reactive oxygen species (ROS) produced by salt-induced oxidative stress, the activities of peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were enhanced. Photosynthetic pigment contents and PSII activity did not significantly decrease under salt stress. The results indicate that the mechanism of salt tolerance in V. trifolia are by ion homeostasis, osmotic balance, antioxidant enzyme induction and photosynthesis adjustment.

A D-pinitol transporter, LjPLT11, regulates plant growth and nodule development in Lotus japonicus

Polyol transporters (PLTs) have been functionally characterized in yeast and Xenopus laevis oocytes as H +-symporters with broad substrate specificity, but little is known about their physiological roles in planta. To extend this knowledge we investigated roles of LjPLT11 in Lotus japonicus-Mesorhizobium symbiosis. Functional analyses of the LjPLT11 in yeast characterized this protein as an energy-independent transporter of xylitol, two O-methyl inositols, xylose and galactose. We also showed that LjPLT11 is located on peribacteroid membranes (PBMs) and functions as a facilitative transporter of D-pinitol within infected cells of L. japonicus nodules. Knockdown of LjPLT11 (LjPLT11i) in L. japonicus accelerated plant growth under nitrogen-sufficiency, but resulted in abnormal bacteroids with corresponding reductions in nitrogenase activity in nodules and plant growth in the nitrogen-fixing symbiosis. LjPLT11i nodules had higher osmotic pressure in cytosol and fewer in bacteroids than wildtype nodules both three and four weeks after inoculation of M. loti. Levels and distributions of reactive oxygen species were also perturbed in infected cells of four-week-old nodules in LjPLT11i plants. The results indicate that LjPLT11 plays a key role in adjustment of levels of its substrate pinitol, and thus maintenance of osmotic balance in infected cells and PBM stability during nodule development.

Cold Regulation of Genes Encoding Ion Transport Systems in the Oligotrophic Bacterium Caulobacter crescentus

Low-temperature stress is an important factor for nucleic acid stability and must be circumvented in order to maintain the basic cell processes, such as transcription and translation. The oligotrophic lifestyle presents further challenges to ensure the proper nutrient uptake and osmotic balance in an environment of slow nutrient flow.

Genome-Wide Analysis of HAK/KUP/KT Potassium Transporter Genes in Banana (Musa Acuminata L.) and Their Tissue-Specific Expression Profiles Under Potassium Stress

Potassium is one of the most essential inorganic cations for plant growth and development. The high affinity K+ (HAK)/K+ uptake (KUP)/K+ transporter (KT) family plays essential roles in the regulation of cellular K+ levels and the maintenance of osmotic balance. However, the roles of these genes in the responses of bananas to low-potassium stress are unclear. In this study, 24 HAK/KUP/KT (MaHAK) genes were identified from banana genomic data. These genes were further classified into four groups based on phylogenetic analysis, gene structure and conserved domain analysis. Segmental duplication events played an important role in the expansion of the MaHAK gene family. Transcriptome analysis revealed the expression patterns of MaHAKs in various tissues under different K+ conditions. MaHAK14b was upregulated under both short- and long-term K+-deficient conditions, suggesting that it plays crucial roles in K+ uptake at low K+ concentrations. Furthermore, MaHAK14b mediated K+ uptake when it was heterologously expressed in the yeast mutant R5421 on low K+ medium. Collectively, these findings provide a foundation for further functional analysis of MaHAK genes, which may be used to improve stress resistance in bananas.