Ethylene modulates root cortical senescence in barley

Root cortical senescence (RCS) is a poorly understood phenomenon with implications for adaptation to edaphic stress. Schneider et al. demonstrate that ethylene modulates RCS.

Root cortical senescence is a type of programmed cell death in cortical cells of several Poaceae species. It might have a role in helping some plants cope with stresses from soil conditions, but it’s not very well studied.

roots in different states of RCS
Roots with and without RCS. Image Schneider et al. 2018

Hannah Schneider and colleagues tested three ideas, that root cortical senescence (RCS) in barley (Hordeum vulgare L.) is:

  1. accelerated by exogenous ethylene exposure
  2. accompanied by differential expression of ethylene synthesis and signalling genes
  3. associated with differential expression of programmed cell death (PCD) genes

To test these hypotheses, the authors evaluated gene expression of root segments from four barley genotypes with and without RCS using quantitative real-time PCR (qRT-PCR). They manipulated the progression of RCS 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).

Writing in Annals of Botany, the authors say: “Understanding the mechanisms and the role of ethylene and PCD in RCS has important implications for breeding and understanding the development of root anatomical traits. Ethylene signalling may serve to modulate the extent and timing of RCS so that root function and metabolic cost can be adjusted in response to environmental conditions such as nutrient deficiencies. The predictable patterns in RCS distribution would permit breeding efforts utilizing RCS for increased edaphic stress tolerance. Genetic variation exists in RCS which could be exploited in breeding programmes.”

Reference List

Schneider, H. M., & Lynch, J. P. (2017). Functional implications of root cortical senescence for soil resource capture. Plant and Soil, 423(1-2), 13–26. https://doi.org/10.1007/s11104-017-3533-1

Schneider, H. M., Wojciechowski, T., Postma, J. A., Brown, K. M., & Lynch, J. P. (2018). Ethylene modulates root cortical senescence in barley. Annals of Botany, 122(1), 95–105. https://doi.org/10.1093/aob/mcy059