Abstract
In the present study, we investigated two Pseudomonas species strains (P. fluorescens SBW25 and P. putida KT2440) for their
use in plant tolerance under salt stressed condition. Barley (Hordeum vulgare L.) plants inoculated with PGPR strains were
subjected to 200mM salinity stress and were analyzed in comparison to non-treated stressed plants based on height, leaf area
and fresh and dry weights of shoots. Our data revealed significant enhancement of root fresh and dry weights, chlorophyll
content and relative water content in PGPR applied plants. Further investigation of various phytohormones (ABA, JA, ethylene,
SA and IAA), stress responsive transporters and antioxidant enzymes genes at molecular level revealed that among the selected
genes of ABA biosynthesis and regulated genes including NCED, DHN5, DRF1 and WRKY18 were significantly downregulated, while P5CS1 and DHN1 genes were significantly up-regulated by PGPR applications. Except LOX2 all the selected
genes (FAD3, LOX1, AOS, AOC, OPR3, PLDα1and PI (SD10)) of JA biosynthesis pathway were significantly up-regulated
by P. putida KT2440 strain. KT2440 strain also significantly induced the expression of ethylene biosynthesis ACCO and ACCS
and SA biosynthesis ICS and protein kinase MAPKK genes. For auxin pathway, P. fluorescens SBW25 strain helped in
significant induction of TDC expression, while P. putida KT2440 strain significantly boosted the expression of T5M gene.
Both PGPR strains, displayed significant down-regulation of NHX1 antiporter, while showed an up-regulation of GR
antioxidant gene. A significant enhanced expression of nitrate transporter NRT2.2, and antioxidant CAT2 genes was observed
in P. fluorescens SBW25 inoculated barley roots compared to control roots. The findings of our study revealed effectiveness
of selected PGPR strains for enhancing salinity tolerance by modulating the expression of major defense mediated pathways,
stress responsive transporters and of antioxidant enzymes genes. Both PGPR strains showed improved effects, but P. putida
KT2440 showed more pronounced significant effects comparatively. Conclusively, these PGPR species are an effective source
of plant stress tolerance and elevated growth of barley plants
N. Shakeel, Sania Zaib , Samina, Imtiaz Ahmad. (2020) MODULATION OF BARLEY (Hordeum vulgare) DEFENSE AND HORMONAL PATHWAYS BY PSEUDOMONAS SPECIES ACCOUNTED FOR SALINITY TOLERANCE, Pakistan Journal of Agricultural Sciences, Volume 57, Issue 6.
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