Research Advances on Cuticular Waxes Biosynthesis in Crops: A Review

Cuticular waxes are the hydrocarbon consisting of very long chain primary alcohols, aldehydes, fatty acids, alkane and esters. They are hydrophobic layer which protect aerial plant organs and help plant species for adaptation in different environments. Wax deposition and chemical composition vary considerably among crop species. Cuticular waxes play a significant role against major abiotic stresses in plants such as drought, high salinity and cold. So, it draws close attention to molecular processes of cuticular wax biosynthesis under stress factors. Here, we briefly summarized to the existing knowledge on the cuticular waxes properties, diversity, morphological changes in leaf surface wax crystals and amount and composition of cuticular waxes. We also provide information about wax biosynthesis genes in crops. Recently, due to progress of plant genome sequence, numerous genes involved in biosynthesis of cuticular waxes have been characterized both for model plant (Arabidopsis) and crops such as rapeseed (Brassica napus), Camelina spp, potato (Solanum tuberosum), eggplant (S. macrocarpon), tomato (S. lycopersicum), barley (Hordeum vulgare), rice (Oryza sativa), maize (Zea mays), wheat (Triticum astivum), broccoli (B. olericea), sesame (Sesamum indicum), tobacco (Nicotiana tabacum), cucumber (Cucumis sativus), cabbage (B. oleracea) etc. Basic compositions of cuticular wax are alcohols, branched alkanes, alkenes, aldehydes, fatty acids, esters, ketones, triterpenoids and sterols in crops. However, they vary from one crop species to the other. Cuticular wax biosynthesis is organ-specific and depends upon developmental stages of crops, and induced by environmental stimuli. The genetic factors also control wax biosynthesis and composition. However, cuticular wax also acts as a photoprotector layer during photosynthesis and protect from UV light radiation. It is also linked to gas exchange and plant development. In this review, we have summarized the cuticular wax amounts and contents in different organs, and genes to be involved in cuicular wax biosynthesis in several crops. This knowledge may be helpful in potential applications for selection of crop for agricultural sustainability.