Transcriptome‐wide identification and analysis of the KT/HAK/KUP family in black goji under NaCl stress

Black goji (Lycium ruthenicum Murr.) is a typical salt-tolerant plant that can maintain normal growth under high NaCl treatment and is distributed in saline areas in northwestern China. The KT/HAK/KUP (KUP) gene family plays an essential role in K absorption and transport process. However, the role of the KUP gene family in the salt tolerance of black goji has not yet been investigated. Therefore, the objective was to identify the members of LrKUPs in black goji by bioinformatics based on Illumina sequencing transcriptome data. Moreover, the expression profiles of LrKUPs under different NaCl treatments were analyzed based on fragments per kilobase of exons per million mapped reads (FPKM) values above 5, using real-time quantitative polymerase chain reaction (RT-qPCR). A total of 31 LrKUPs were identified, and 19 LrKUPs containing the same K+ transporter domain were used to construct a phylogenetic tree and classified into four clusters. Six LrKUPs with full-length sequences were discovered by open reading frame (ORF). They were localized to the plasma membrane and the predicted transmembrane regions were 12-14. The selected LrKUPs exhibited different expression patterns under NaCl stresses. It is noteworthy that LrKUPs (-4, -9, -11, -31) from leaves and stems could withstand higher concentration and longer duration of salt stress compared with roots. In the present study, the KUP gene family was discovered as a potential stress resistance regulator for black goji growth and development, this provides candidate genes for future functional research of LrKUPs.