Enhancement of very-long-chain cuticular wax biosynthesis triggered by water loss in response to pericarp senescence in litchi fruit

Litchi ( Litchi chinensis Sonn.) is sensitive to water loss in early detached stage, which triggers oxidative stress and cellular damage inducing pericarp browning. This study analyzed surface wax metabolism in litchi fruit via lipid profiling, gene expression analysis, and overexpression in tomato lines to investigate its response to water loss. The rapid water loss of litchi fruit was largely from pericarp accompanied with the development of gold-brown appearance under unpacked conditions. To response the water loss and browning process, genes involved in biosynthesis of cuticular waxes were upregulated following the increased accumulation of very-long-chain aliphatic compounds on exocarp surface. The candidate genes LcLACS4 and LcWAX2 localized to the endoplasmic reticulum, where is the main position for wax biosynthesis. Heterologous expression of LcLACS4 and LcWAX2 both enhanced drought tolerance for tomato plant, increased the accumulation of cuticular waxes, particularly very-long-chain aldehydes and n -alkanes, as well as decreased water loss of tomato fruit. These findings demonstrate that the alteration of very-long-chain cuticular wax may play important role in response to the water loss of fruit, thereby influencing the browning of litchi. It also provides insights to link between cuticular wax metabolism and the regulation changes in senescence of harvest litchi fruit. • Litchi fruit is highly susceptible to water loss, leading to pericarp browning. • Water loss triggers upregulation of wax biosynthesis genes and increase of VLC wax deposition. • Functional validation in tomato confirms conserved wax-related drought tolerance and enhanced transpiration barrier. • Cuticular wax composition influences fruit transpiration indirectly modulating browning senescence in litchi.