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RESEARCH PRODUCT

Increased Auxin Content and Altered Auxin Response in Barley Necrotic Mutant nec1

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The role of hormone crosstalk in plant immunity is lately emerging as significant topic of plant physiology. Although crosstalk between salicylic acid and auxin affects plant disease resistance, molecular mechanisms of this process have not yet been uncovered in details. Mutations disrupting cyclic nucleotide-gated ion channel 4 (CNGC4) affect SA-mediated disease resistance in barley Hordeum vulgare and in A. thaliana. Significantly, decreased stomatal apertures of barley CNGC4 mutant nec1 and dwarfed stature of A. thaliana CNGC4 mutant dnd2 suggest that nonfunctional CNGC4 might be affecting also auxin signaling. Excised coleoptile elongation, stomatal conductance, and cell size measurements assaying physiological effect of exogenous auxin treatment suggested altered auxin signaling in nec1 mutant. Real-time qPCR analysis identified significant change in mRNA abundance of four auxin-related genes – YUCCA1, VT2, HVP1, and TIR1. Analysis of endogenous auxin content of nec1 plants detected ca. fourfold increase in indole acetic acid (IAA) content in nec1 leaves and roots compared to wt plants, as measured by HPLC. These results suggest that apart from SA-related disease resistance, CNGC4 functions also in auxin signaling in barley; therefore, barley nec1 mutant could serve as model system revealing role of SA-auxin crosstalk in plant disease resistance.