Both aluminum and ABA induce the expression of an ABC-like transporter gene (FeALS3) in the Al-tolerant species Fagopyrum esculentum

- The expression of a gene encoding an ABC transporter-like protein is described.
- ABA increases if Al exposure exceeds the threshold level for Al exclusion and causes cell damage.
- This increase in ABA correlates with the expression of the ABC-like gene ALS3 (FeALS3).
- FeALS3 might be required for Al resistance in the early responses to Al toxicity.

Aluminum (Al) toxicity in acid soils limits crop potential on a global scale. Buckwheat (Fagopyrum esculentum) is a highly Al-tolerant crop. Genes from Al-inducible malate transporter (ALMT), multidrug and toxic compounds extrusion (MATE), and ABC transporter-like gene (ALS3) are implicated in Al-tolerance in a variety of plants. Yet no genes have been related to Al resistance in buckwheat. This study addresses for the first time the question whether ALS3 gene encoding a transmembrane domain homologous to a bacterial ABC protein that has been involved in Al tolerance of Arabidopsis thaliana might also be implicated in the activation of Al tolerance in buckwheat. Furthermore, the possible role of ABA in the expression of this gene is considered. A cDNA clone corresponding to a FeALS3 was characterized. qPCR analysis showed that FeALS3 expression is constitutive but increases with Al concentrations above the toxicity threshold. Results reveal that initially, when Al exposure exceeds the threshold level for Al exclusion and causes cell damage, ABA levels increase. This increase correlates with the expression of gene FeALS3. The same was observed when exogenous ABA was supplied to controls without Al. Al-induced enhancement of FeALS3 expression matched the recovering of the relative root growth rate. We propose that in buckwheat an Al concentration above the toxicity threshold promotes Al detoxification either by activating FeALS3 directly or by stimulating elevated levels of ABA.