Ethylene Modulates Root Cortical Senescence in Barley


Hannah M. Schneider, Tobias Wojciechowski, Johannes A. Postma, Kathleen M. Brown, and Jonathan P. Lynch


Annals of Botany, in press

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Background and Aims: 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 signaling genes; 3) associated with differential expression of programmed cell death (PCD) genes.

Methods: Gene expression of root segments from four barley genotypes with and without RCS was evaluated using qRT-PCR. The progression of RCS was manipulated with root-zone ethylene and ethylene inhibitor applications.

Key Results:  Results demonstrate that ethylene modulates RCS. Four genes related to ethylene synthesis and signaling 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 to the control aeration treatment in seminal and nodal roots, respectively. RCS was correlated with expression of two genes related to PCD.

Conclusions: The development of RCS is similar to root cortical aerenchyma formation with respect to ethylene modulation of the PCD process.