Identification of Catalpa bungei Aquaporin Gene Family Related to Low Temperature Stress

Abstract

Low temperatures pose a significant threat to plant growth and development. Studies have shown that aquaporins (AQPs), as the main functional proteins on the cell membrane regulating water ingress and egress, play a vital role in maintaining dynamic water balance when plants face cold stress. Catalpa bungei, an important timber and ornamental tree species, has its cultivation range significantly limited by its poor cold tolerance. However, no study has been found aiming to identify its aquaporin gene family. This study aims to fill this gap using two C. bungei cultivars with differing cold tolerance as experimental material: “Qiuza 1”, which is less cold-tolerant, and “Qiuza 2”, which is more cold-tolerant. The plants were subjected to low-temperature stress at 4 °C for 24 h. Using high-throughput molecular sequencing technology, a transcriptome sequencing of the leaves was performed at 0, 6, 12, and 18 h of cold stress. Fifteen candidate aquaporin genes in C. bungei (CbAQP) were identified. Phylogenetic analysis showed that the CbAQP gene family is divided into five subfamilies: 5 PIPs, 4 TIPs, 3 NIPs, 2 SIPs, and 1 XIP. By analyzing AQPs related to cold stress in other plants and the expression patterns of CbAQP genes, 12 CbAQP genes related to cold stress were identified. The genes that responded positively include CbPIP2;5, CbPIP1;2, CbTIP4;1, and CbNIP2;1. The results provide a foundation for further analysis of the biological functions of candidate CbAQP genes related to cold tolerance and offer theoretical support for improving seedling quality, cold-resistant genetic breeding, and expanding its distribution range.