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Ethylene modulates root cortical senescence in barley

Schneider, Hannah M, Wojciechowski, Tobias, Postma, Johannes A, Brown, Kathleen M, Lynch, Jonathan P
Annals of botany 2018 v.122 no.1 pp. 95-105
Hordeum vulgare, aeration, aerenchyma, barley, ethylene, ethylene inhibitors, gene expression regulation, genes, genotype, nitrogen, phosphorus, programmed cell death, quantitative polymerase chain reaction, reverse transcriptase polymerase chain reaction, rhizosphere, roots
Root cortical senescence (RCS) is a poorly understood phenomenon with implications for adaptation to edaphic stress. It was hypothesized that RCS in barley (Hordeum vulgare L.) is (1) accelerated by exogenous ethylene exposure; (2) accompanied by differential expression of ethylene synthesis and signalling genes; and (3) associated with differential expression of programmed cell death (PCD) genes. Gene expression of root segments from four barley genotypes with and without RCS was evaluated using quantitative real-time PCR (qRT-PCR). The progression of RCS was manipulated with root zone ethylene and ethylene inhibitor applications. The results demonstrate that ethylene modulates RCS. Four genes related to ethylene synthesis and signalling were upregulated during RCS in optimal, low nitrogen and low phosphorus nutrient regimes. RCS was accelerated by root zone ethylene treatment, and this effect was reversed by an ethylene action inhibitor. Roots treated with exogenous ethylene had 35 and 46 % more cortical senescence compared with the control aeration treatment in seminal and nodal roots, respectively. RCS was correlated with expression of two genes related to programmed cell death (PCD). The development of RCS is similar to root cortical aerenchyma formation with respect to ethylene modulation of the PCD process.