Increased cuticular wax accumulation and enhanced drought tolerance in transgenic alfalfa (Medicago sativa) by overexpression of a transcription factor gene

Plant cuticular waxes play an important role in protecting aerial organs from damage caused by multiple environmental stresses such as drought, cold, UV radiation, pathogen infection, and insect attack. We characterized a novel AP2 domain-containing transcription factor gene, designated WXP1, from the model legume plant Medicago truncatula. The gene is able to activate wax production and confer drought tolerance in alfalfa (Medicago sativa). The predicted protein of WXP1 has 371 aa; it is one of the longest peptides of all the single AP2 domain proteins in M. truncatula. Transcript level of WXP1 is inducible by cold, ABA and drought treatment in shoot tissues. Overexpression of WXP1 under the control of CaMV35S promoter led to a significant increase in cuticular wax loading on leaves of transgenic alfalfa. Transgenic leaves showed reduced water loss and chlorophyll leaching. Transgenic alfalfa plants with increased cuticular waxes showed enhanced drought tolerance demonstrated by delayed wilting after watering was ceased and quicker and better recovery when the dehydrated plants were re-watered.