Improved Drought Stress Response in Alfalfa Plants Nodulated by an IAA Over-producing Rhizobium Strain
Articolo
Data di Pubblicazione:
2017
Citazione:
Improved Drought Stress Response in Alfalfa Plants Nodulated by an IAA Over-producing Rhizobium Strain / R. Defez, A. Andreozzi, M. Dickinson, A. Charlton, L. Tadini, P. Pesaresi, C. Bianco. - In: FRONTIERS IN MICROBIOLOGY. - ISSN 1664-302X. - 8(2017 Dec 14), pp. 2466.1-2466.13. [10.3389/fmicb.2017.02466]
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.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
rhizobium; legume; nitrogen fixation; drought stress; indole-3-acetic acid; ABA; ethylene; photosynthesis
Elenco autori:
R. Defez, A. Andreozzi, M. Dickinson, A. Charlton, L. Tadini, P. Pesaresi, C. Bianco
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