A unique aluminum resistance mechanism conferred by aluminum and salicylic-acid-activated root efflux of benzoxazinoids in maize
Background and aims
Although aluminum (Al) exclusion via root exudation of organic matters is a common resistance mechanism adopted by many plant species, whether root exudation of benzoxazinoids, such as hydroxamic acids (HAs), confers Al resistance remains unclear.
We performed physiological characterization for an Al-resistant maize cultivar TY and a sensitive maize cultivar ZD.
First, Al exposure induced HA exudation from the root tip of TY, but not from ZD. Second, HAs formed non-toxic Al chelation complexes in vitro and exogenous HAs alleviated root damage and improved root growth under Al stresses. Third, both Al and exogenous salicylic acid (SA) treatments induced accumulation of endogenous SAs in the root apices of TY, which in turn enhanced root HA exudation and Al resistance in TY. Furthermore, an SA biosynthesis inhibitor significantly decreased Al resistance in TY and abolished the beneficial effects of exogenous SA on Al resistance, suggesting a key role of the endogenous SAs in induction of Al resistance. Finally, it was the root-tip HA exudation but not the root-tip HA contents that determined Al resistance in maize.
We have revealed a unique Al exclusion mechanism underlying Al resistance via Al and SA-mediated root HA efflux in maize.
KeywordsAluminum tolerance Benxozaxinoids Hydroxamic acids Maize Root exudate Salicylic acid
This study is supported by the National Natural Science Foundation of China (grant NO. 31201680) and Guangxi Natural Science Foundation (grant NO. 2012GXNSFAA053047 and NO. 2016GXNSFAA380230).
This study was conceived and supervised by XL, MG, ZZ, JL and XT; XG, YK, MC and LX performed the experiments. The manuscript was written by ZZ, XT and JL and was reviewed by all authors.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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