Journal of Experimental Botany

30 May 2019 - By: Jonathan Ingram

Salt tolerance in polyploids

Sensitivity of root zone channels to H2O2 is central to salinity tolerance in polyploids

 

Liu Y, Yu Y, Sun J, et al. 2019. Root-zone-specific sensitivity of K+ and Ca2+-permeable channels to H2O2 determines ion homeostasis in salinized diploid and hexaploid Ipomoea trifida. Journal of Experimental Botany, 70, 1389–1405.

https://bit.ly/2BVxrO1

 

Shabala S. 2019. Linking ploidy level with salinity tolerance: NADPH-dependent ‘ROS– Ca2+ hub’ in the spotlight. Journal of Experimental Botany, 70, 1063–1067.

https://bit.ly/2BQjEYU

 

Why are polyploids generally more salt tolerant than their diploid progenitors? It is a particularly interesting question given the critical role of polyploidisation in plant evolution together with the large number of polyploid crops, including wheat, sweet potato, and oilseed rape. Yang Liu et al examined this question in the wild sweet potato Ipomoea trifida, the closest relative of the widely grown hexaploid (6x) crop. I. trifida has a range of ploidy levels, making it ideal for comparative studies. Here patterns of ion flux were examined in the 6x and 2x forms subjected to salt and reactive oxygen species (ROS). Using non-invasive micro-test technology, (NMT) it was shown that the sensitivity of K+- and Ca2+-permeable channels to H2O2 is central to improved K+/Na+ homeostasis. Differences in the root zone plasma membrane enabling improved tolerance included reduced sensitivity of K+-channels and increased sensitivity of Ca2+-channels, conferring better K+ retention and Na+ exclusion during salt stress. The authors also showed that K+ efflux was significantly reduced in the diploid line by diphenylene iodonium, which inhibits NADPH oxidase and together with wider evidence suggests an important role for this enzyme. Picking up on this in a commentary, Shabala argues that Ca2+-activated NADPH oxidases and ROS-activated Ca2+-permeable cation channels form a critical ‘ROS–Ca2+ hub’. It is also hypothesised that polyploids might encode chimeric non-selective cation channels, explaining the desensitisation observed.

Jonathan Ingram, Commissioning Editor, Journal of Experimental Botany

Category: Plant Biology
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