Tomato SlCER1–1 catalyzes the synthesis of wax alkanes, increasing drought tolerance and fruit storability

Very-long-chain (VLC) alkanes are the main wax compounds of tomato fruits and leaves. ECERIFERUM1 (CER1) and ECERIFERUM3 (CER3) are the two key genes involved in VLC alkane biosynthesis in Arabidopsis thaliana. However, CER1 and CER3 homologs have not been investigated in tomato, and their exact biological functions remain unknown. We analyzed the wax profiles of tomato leaves and fruits at different growth stages and characterized the tomato CER1 and CER3 homologs. VLC alkanes were the predominant wax compounds in both leaves and fruits at all developmental stages. We identified five CER1 homologs and two CER3 homologs in tomato, which were designated SlCER1–1 to SlCER1–5 and SlCER3–1 and SlCER3–2, respectively. The genes exhibited tissue- and organ-specific expression patterns and were induced by abiotic stresses. SlCER1–1 was localized to the endoplasmic reticulum (ER), which is also the main site of wax biosynthesis. Silencing SlCER1–1 in tomato significantly reduced the amounts of n-alkanes and branched alkanes, whereas its overexpression in Arabidopsis had the opposite effect. Under drought stress, both n-alkanes and branched alkanes increased significantly in wild-type but not SlCER1–1 RNAi tomato plants. Furthermore, SlCER1–1 silencing also increased the cuticular permeability of leaves and fruits. In conclusion, SlCER1–1 is involved in wax alkane biosynthesis in tomato and plays an important role in drought tolerance and fruit storability.