Drought is an adverse environmental factor for plant growth and development. Aquaporins play an influential role in water uptake and transport in plants. However, the function of PagPIP2;10 in response to drought stress remains largely unclear. Here, we report that the plasma membrane intrinsic protein PagPIP2;10 was in the cell membrane and induced by dehydration in the poplar 84K hybrids. The overexpression of PagPIP2;10 in poplars enhanced drought tolerance. The PagPIP2;10ox lines maintained a higher water retention content, photosynthetic rate, and proline content. Meanwhile, a lower content of MDA and transpiration and stomatal conductance were observed under drought stress than in that of the WT plants. A further analysis found that the PagPIP2;10ox lines decreased the stomatal aperture and accumulated more ROS in guard cells compared with WT after ABA treatment with the exception that the root hydraulic conductance of the PagPIP2;10ox lines was higher than that of the WT plants. These results imply that PagPIP2;10 played a positive role in enhancing drought stress via enhancing water-retaining capacity under drought stress.

Flavonoids are an important type of bioactive substance contained in jujubes. Flavonol synthase (FLS) is a key enzyme for the synthesis of flavonoids such as flavonols and anthocyanins. To study the biological functions of FLS in jujubes, we cloned the ZjFLS gene; analyzed its physicochemical properties and evolutionary relationships; and then conducted an expression characteristic analysis, subcellular localization, prokaryotic expression and heterologous overexpression in Arabidopsis thaliana. The results showed that the length of ZjFLS is 951 bp, and it encodes 316 amino acids. A sequence analysis revealed that ZjFLS exhibited a high degree of conservation in evolution. The results of a qRT-PCR analysis indicated that the ZjFLS gene could be expressed in different tissues of jujube: the expression level was the highest in the leaves, followed by the flowers, and the lowest was in the fruits. Within these expression levels, it was higher in young leaves than in mature leaves and higher in the white-ripe-stage fruits than in the semi-red-stage fruits. Subcellular localization indicated that the ZjFLS gene was located in the nucleus, cytoplasmic matrix, and cytoplasmic membrane. Our research findings show that the ZjFLS protein can be induced and obtained in the prokaryotic expression system and successfully purified. It mainly exists in the form of inclusion bodies and has a relatively low content in the soluble supernatant. The total flavonoid content of Arabidopsis thaliana strains with a heterologous overexpression of the ZjFLS gene was significantly higher than that of the wild type, confirming that the ZjFLS gene can promote the biosynthesis of flavonoid substances.