Transplanting experiment and transcriptome sequencing reveal the potential ecological adaptation to plateau environments in the allopolyploid Isoetes sinensis

Abstract

Relatively high frequencies of polyploidy are generally found in high-altitude regions. However, more diploid than polyploid species of Isoetes are distributed in plateau environments in China. The low-altitude species Isoetes sinensis originates from the allopolyploidization between a plateau parent and another low altitude species. To study potential ecological adaptation to plateau environments in the allopolyploid I. sinensis, we transplanted individuals of I. sinensis to different altitudes. RNA sequencing was performed to elucidate the molecular response of this species’ ecological adaptation to plateaus. More unique differentially expressed genes (DEGs) were detected in individuals transplanted to the Qinghai–Tibet Plateau (QTP) than elsewhere, such as genes for ribosomal proteins (RPs) and succinate dehydrogenase (SDH), which helped them adapt to higher altitudes under both terrestrial and submerged conditions. In both terrestrial and submerged conditions, the expression of a large number of genes changed to help plants adapt to exposure to the high levels of ultraviolet (UV) radiation on plateaus, such as the genes associated with the accumulation of flavonoids, decreasing chlorophyll content, and reducing light harvesting activity. The expression of vacuolar-type H+-transporting ATPase (V-ATPase) and phosphoenolpyruvate carboxylase (PEPC) increased with altitude, revealing that the intensity of the crassulacean acid metabolism (CAM) of I. sinensis might be positively associated with altitude. In general, our results reveal that although I. sinensis only lives at low altitudes, it can still adapt to plateau stress by regulating the expression of certain key genes. The potential ecological adaptation to plateau environments in the allopolyploid I. sinensis may have been inherited from the plateau parent.