Comparative analyses of leaf cuticular lipids of two succulent xerophytes of the Ordos Plateau (Gobi Desert), Tetraena mongolica maxim and Zygophyllum xanthoxylum (Bunge) Engl

Abstract Tetraena mongolica Maxim, a relic shrub of the paleo-Mediterranean flora, is normally accompanied in the Western Ordos desert by another plant species in the same taxonomic family, Zygophyllum xanthoxylum (Bunge) Maxim, and together they play a vital role in the ecology of the local environment. Z. xanthoxylum has been identified as having stronger drought tolerance than T. mongolica. As an important water barrier, cuticles were compared between these two relatives to better reveal the mechanism of their different drought tolerance. Z. xanthoxylum possesses more flattened wax crystals, lower epidermal permeability and higher water use efficiency (WUE) than T. mongolica. The composition of cuticular lipids were analyzed, and the results showed that Z. xanthoxylum had significantly higher total amounts of both cuticular wax and cutin monomers than T. mongolica, with all wax class (especially alkanes) and cutin monomer amounts being much higher in Z. xanthoxylum. Cuticle-associated genes were analyzed by transcriptome sequencing, and the results showed that more alkane synthesis genes were up-regulated in Z. xanthoxylum. These findings provide different cuticles on these two succulent xerophytes and reveal the relationships with their different drought tolerance. This study is helpful to reveal the function of plant cuticle in adaptability to extreme environments.