Improved Drought Stress Response in Alfalfa Plants Nodulated by an IAA Over-producing Rhizobium Strain

Abstract

The drought–stress response in plant involves the cross-talk between abscisic acid (ABA) and other phytohormones, such as jasmonates and ethylene. The auxin indole-3-acetic acid (IAA) plays an integral part in plant adaptation to drought stress. Investigation was made to see how the main auxin IAA interacted with other plant hormones under water stress, applied through two different growth conditions (solid and hydroponic). Medicago sativa plants nodulated by the Ensifer meliloti wild type 1021 (Ms-1021) and its IAA-overproducing RD64 derivative strains (Ms-RD64) were subjected to drought stress, comparing their response. When the expression of nifH gene and the activity of the nitrogenase enzyme were measured after stress treatments, Ms-RD64 plants recorded a significantly weaker damage. These results were correlated with a lower biomass reduction, and a higher Rubisco protein level measured for the Ms-RD64-stressed plants as compared to the Ms-1021-stressed ones. It has been verified that the stress response observed for Ms-RD64-stressed plants was related to the production of greater amount of low-molecular-weight osmolytes, such as proline and pinitol, measured in these plants. For the Ms-RD64 plants the immunoblotting analysis of thylakoid membrane proteins showed that some of the photosystem proteins increased after the stress. An increased non-photochemical quenching after the stress was also observed for these plants. The reduced wilting signs observed for these plants were also connected to the significant down-regulation of the MtAA03 gene involved in the ABA biosynthesis, and with the unchanged expression of the two genes (Mt-2g006330 and Mt-8g095330) of ABA signaling. When the expression level of the ethylene-signaling genes was evaluated by qPCR analysis no significant alteration of the key positive regulators was recorded for Ms-RD64-stressed plants. Coherently, these plants accumulated 40% less ethylene as compared to Ms-1021-stressed ones. The results presented herein indicate that the variations in endogenous IAA levels, triggered by the overproduction of rhizobial IAA inside root nodules, positively affected drought stress response in nodulated alfalfa plants.

Row spacing of alfalfa interseeded into native grass pasture influences soil‐plant‐water relations

“…However, a few studies reported differences between cultivars in efficiency of using soil water (Dobrenz, Wright, Humphrey, Massengale, & Kneebone, 1969;Grimes, Wiley, & Shesley, 1992). Anatomical and morphological differences in growth types generally influence alfalfa water use and capability to tolerate water deficit or cold by expressing fall dormancy (Paquin & Mehuys, 1980), reducing leaf size (Jung & Larson, 1972), and deepening root elongation (Defez et al, 2017).…”

Physiological characterization and thylakoid ultrastructure analysis in super high-yield hybrid rice leaves under drought stress

“…ABA is considered to be an important messenger involved in the adaptive response of plants against abiotic and biotic stresses (Umezawa et al 2006). ABA and IAA can improve plant drought-stress tolerance (Sreenivasulu et al 2012, Defez et al 2017. In this study, there was a slight increase but no significant difference in IAA compared with the WW group during drought stress, which may be attributed to the complexity of IAA biosynthesis regulation or/and the uniqueness of rice LYPJ.…”

ФИЗИОЛОГИЧЕСКИЕ И ГЕНЕТИЧЕСКИЕ МЕХАНИЗМЫ ОТВЕТА ЧАЙНОГО РАСТЕНИЯ Camellia sinensis (L.) Kuntze НА ЗАСУХУ

“…По-видимому, увеличение содержания цитокининов может частично смягчать негативное влияние стресса на фотосинтетическую активность и замедлять ускоренное старение листьев (36). О с м о л и т ы. Еще одной стратегией адаптации к засухе служит повышение синтеза осмолитов -растворенных в цитозоле веществ с низкой молекулярной массой, которые даже в высоких концентрациях не токсичны для растения (37)(38)(39). Осмолиты повышают вязкость цитоплазмы, поглощают активные формы кислорода и защищают макромолекулы от свободных радикалов, тем самым поддерживая целостность мембран и метаболическую активность тканей, что обеспечивает возобновление роста после улучшения водного режима (40)(41)(42).…”

“…А н т и о к с и д а н т н ы е к о м п о н е н т ы. Системы антиоксидантной защиты включают как ферментный (СОД, каталазу, пероксидазу, аскорбат-пероксидазу, глутатион-редуктазу), так и неферментный (цистеин, редуцированный глутатион и аскорбиновую кислоту) компоненты (27,37,52). Установлено, что кроме каталазы, различных пероксидаз и пероксидоксинов (25,53,46), еще несколько ферментов вовлечены в процесс избавления от перекиси водорода и свободных радикалов: дегидроаскорбатредуктаза, монодегидроаскорбат-редуктаза, глутатион-редуктаза (31,54).…”

“…Исследователи предположили, что растение чая сохраняет поставки АТФ посредством поддержания гликолитического метаболизма (26). Выявлена роль -каротина в защите от окислительного стресса и поддержании фотохимических процессов (55,56), которая предположительно заключается в прямом гашении триплетного хлорофилла, что препятствует образованию активных форм кислорода (37). Д р у г и е с и г н а л ь н ы е п у т и. Группа молекулярных мессенджеров, регулирующих работу генов ответа, очень многочисленна.…”