Abstract
Drought-resistant plants exhibit strong water retention capability. In this regard, the autotetraploid sour jujube leaves exhibit better water retention than diploid leaves. Morphological comparisons and physiological comparisons of diploid and autotetraploid leaves showed that the autotetraploid leaves had thicker leaf cuticles and more leaf wax accumulation than the diploid leaves, which could reduce cuticle permeability and improve the drought tolerance of leaves. In this study, the cuticular wax crystalloids on the adaxial and abaxial sides of young and mature jujube leaves were observed in the two ploidy types, and unique cuticular wax crystalloids covering a large area of the cuticle on autotetraploid sour jujube leaves may provide an advantage in reducing leaf non-stomata transpiration and improving plant drought tolerance. Based on the transcriptome, 115 differentially expressed genes between diploids and autotetraploids were further analyzed and found to be involved in the accumulation of cuticular wax components, including terpenoids, fatty acids, and lipids, as well as ABC transporter and wax biosynthetic process. Finally, 14 genes differentially expressed between glossy autotetraploid leaves and nonglossy diploid leaves, such as LOC107414787, LOC107411574 and LOC107413721, were screened as candidate genes by qRT-PCR analysis. This findings provided insights into how polyploidization improved drought tolerance.
