Arabidopsis acyl-CoA-binding proteins confer protection against biotic and abiotic stresses

Abstract

Sessile organisms such as plants have evolved to survive adverse conditions imposed by biotic and abiotic stresses, including pathogen invasion, extremes in temperature and drought conditions. The identification of proteins that are switched on during stress treatments represents a first step towards understanding theirfunctions and their potential in genetic engineering. In the model plant, Arabidopsis thaliana, some acyl-CoA-binding proteins (ACBPs) were observed to be upregulated by various stresses. When these ACBPs were expressed ectopically in transgenic plants, theplants were showed protection against the corresponding stresses. The six Arabidopsis ACBPs of the AtACBP family (designated AtACBP1 to AtACBP6),are conserved at the acyl-CoA-binding domainand are distributed acrossfour classes: Class I is represented by the 10-kDa AtACBP6, Class II ACBPs contain ankyrin repeats (AtACBP1 and AtACBP2), Class III is larger (39.4-kDa AtACBP3) and Class IV members are the largest and contain kelch motifs (AtACBP4 and AtACBP5). The ankyrin repeats and kelch motifs in AtACBPs can potentially mediate interactionwith protein partners. Interestingly, several protein partners of ACBPs were also stress-induced proteins. Investigations using Arabidopsis T-DNA insertional mutants and transgenic Arabidopsis AtACBP-overexpressors further support AtACBP function in protection against stress treatments. AtACBP1-and AtACBP2-overexpressors were more resistant to heavy metal/oxidative stress, AtACBP2-overexpressors were drought tolerant, AtACBP3-overexpressors were protected against biotic stress and AtACBP6-overexpressors were freezing tolerant. In vitroassays have revealed that (His)-tagged AtACBPs bind acyl-CoA esters. Thus, the lipid-binding properties and lipid-trafficking abilities of AtACBPs likely enhance plant membranes, which consist oflipid components, to better withstand stresstreatments