Abstract
The effects of whole-genome duplication span multiple levels. Previous study reported that the autotetraploid sour jujube exhibited superior drought tolerance than diploid. However, the difference in water transport system between diploids and autotetraploids and its mechanism remain unclear. Here, we found the number of xylem vessels and parenchyma cells in autotetraploid sour jujube increased to nearly twice that of diploid sour jujube, which may be closely related to the differences in xylem vessel differentiation-related ZjVND7 targets between the two ploidy types. Although the five enriched binding motifs are different, the most reliable motif in both diploid and autotetraploid sour jujube was CTTNAAG. Additionally, ZjVND7 targeted 236 and 321 genes in diploids and autotetraploids, respectively. More identified targeted genes of ZjVND7 were annotated to xylem development, secondary wall synthesis, cell death, cell division, and DNA endoreplication in autotetraploids than in diploids. SMR1 plays distinct roles in both proliferating and differentiated cells. Under drought stress, the binding signal of ZjVND7 to ZjSMR1 was stronger in autotetraploids than in diploids, and the fold-changes in the expression of ZjVND7 and ZjSMR1 were larger in the autotetraploids than in the diploids. These results suggested that the targeted regulation of ZjVND7 on ZjSMR1 may play valuable roles in autotetraploids in the response to drought stress. We hypothesized that the binding of ZjVND7 to ZjSMR1 might play a role in cell division and transdifferentiation from parenchyma cells to vessels in the xylem. This regulation could prolong the cell cycle and regulate endoreplication in response to drought stress and abscisic acid, which may be stronger in polyploids.
Highlights
As important drivers of evolution, almost all eukaryotic genome sequences bear evidence of ancient whole-genome duplications events (Adams and Wendel, 2005)
We reanalyzed the genes that were the differential expression of genes involved in xylem differentiation, secondary cell wall development, cell cycle cell division, and cell death and that were differentially expressed between diploid and autotetraploid leaves
The results showed that both ZjSMR1 and ZjVND7 were responsive to abscisic acid (ABA) treatment
Summary
As important drivers of evolution, almost all eukaryotic genome sequences bear evidence of ancient whole-genome duplications events (Adams and Wendel, 2005). After whole-genome doubling, gene dose effects, modified regulatory interactions, and rapid genetic and epigenetic modifications and changes strongly affect the genome (Jackson and Chen, 2010). These changes affect gene expression, resulting in differences in traits such as those related to morphology, physiology, and adaptability (Allario et al, 2013; Zhang et al, 2015). In the duplicated genome, paralogous copies may acquire a new function (neofunctionalization), several functions controlled by ancestral genes may be partitioned between duplicated genes (subfunctionalization), and redundant copies may accumulate mutations and lose their function, becoming pseudogenes (non-functional). A careful study of the target genes of TFs and their expression patterns will reveal the evolutionary mode of autopolyploid variation and shed new light on the corresponding regulatory network
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