Deciphering the core shunt mechanism in Arabidopsis cuticular wax biosynthesis and its role in plant environmental adaptation.

Plant cuticular waxes serve as highly responsive adaptations to variable environments. Aliphatic waxes consist of very-long-chain (VLC) compounds produced from 1-alcohol- or alkane-forming pathways. The existing variation in 1-alcohols and alkanes across Arabidopsis accessions revealed that 1-alcohol amounts are negatively correlated with aridity factors, whereas alkanes display the opposite behaviour. How carbon resources are allocated between the 1-alcohol and alkane pathways responding to environmental stimuli is still largely unknown. Here, in Arabidopsis, we report a novel 1-alcohol biosynthesis pathway in which VLC acyl-CoAs are first reduced to aldehydes by CER3 and then converted into 1-alcohols via a newly identified putative aldehyde reductase SOH1. CER3, previously shown to interact with CER1 in alkane synthesis, is identified to interact with SOH1 as well, channelling wax precursors into either alcohol- or alkane-forming pathways, and the directional shunting of these precursors is tightly regulated by the SOH1-CER3-CER1 module in response to environmental conditions.