Tandem duplication contributed to adaptation to plateau environment
Although Orinus and Cleistogenes shared the same paleo-allotetraploidy event, O. kokonorica has experienced severe gene loss (large number of contracted gene families) compared withC. songorica during its adaptation to the high plateau. We found only 47.82% (23,240) of gene duplications resulted from WGD/segmental duplication. There was a considerable number of duplicated genes generated from dispersed duplication (22.37%, 10,873), proximal duplication (5.10%, 2477) and tandem duplication (4.10%, 1993) (Figure 2D). We found that the tandem duplicated genes in O. kokonoricawere enriched in many GO terms related to adaptation to the plateau environment, such as ‘cellular response to oxygen levels’, ‘leaf senescence’, ‘aging’, ‘programmed cell death involved in cell development’ and ‘defense response’ (Figure 2E).