Plant cuticular waxes serve as highly responsive adaptations to variable environments1–7. Aliphatic waxes consist of very-long-chain (VLC) compounds produced from 1-alcohol- or alkane-forming pathways5,8. 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.
