Genome-wide identification of LHT gene family in Lonicera macranthoides Hand.-Mazz and their responses to abiotic stresses

Abstract

Amino acid transporters (AATs) allow the transport of amino acids and play important roles in the various physiological processes and environmental responses of plants. The lysine and histidine transporter (LHT) subfamily is an important type of AAT. However, a genome-wide overview of the LHT gene family has not been conducted in L. macranthoides Hand.-mazz. In this study, 11 LHT genes were identified in the Lonicera macranthoides genome. To further understand the functions of LmLHT genes, the gene and protein characteristics, transmembrane helices, evolutionary relationships, chromosomal distribution, cis-acting elements of promoters, and expression patterns were systematically analyzed. According to the results, LmLHT genes were divided into two groups based on the phylogenetic analysis. Transmembrane helices of LmLHT proteins ranged from seven to 16. Gene structure and conserved motif analysis revealed that exon-intron structures and motifs were relatively conserved in the LmLHT family. LmLHT genes were distributed on six of the nine chromosomes and had the most collinear gene pairs with NtLHT genes. Additionally, phytohormones, low-temperature, drought-inducibility, defense and stress related cis-acting elements were enriched in the promoters of LmLHT genes. LmLHT genes showed distinct or preferential expression patterns in various tissues, signifying their potential roles in plant growth and development. We also found that some LmLHT genes were responsive to cold and drought stresses, indicating their roles in abiotic stress adaptation. Overall, our results provided comprehensive insight into the LmLHT gene family and will be useful for future functional analyses.

Keywords: AAT; LHT; Lonicera macranthoides Hand.-mazz; abiotic stresses; genome-wide.

FIGURE 1

Phylogenetic analysis of LHT proteins in Lonicera macranthoides, tobacco, rice and Arabidopsis. The tree divides 11 LHT proteins from Lonicera macranthoides, 23 LHT proteins from tobacco, 6 LHT proteins from rice, and 10 LHT proteins from Arabidopsis into two subgroups. Black, red, blue, and green colors represent Lonicera macranthoides, tobacco, rice and Arabidopsis, respectively.

FIGURE 2

Evolutionary relationship, gene structure and motif analysis of LmLHT family members. (A) The phylogenetic tree was built from LmLHT proteins. The LmLHT protein sequences were divided into two subfamilies: green and yellow colors indicate subfamily Ⅰ and subfamily Ⅱ, respectively. (B) Exon–intron organization of LmLHT genes. Brown boxes represent exons, and block lines represent introns. (C) Conserved motifs of LmLHT proteins. The motifs are displayed in different colored boxes.

FIGURE 3

Chromosomal locations of LmLHT family members.

FIGURE 4

Collinearity analysis of LHT family members between Lonicera macranthoides (Lm), tobacco (Nt), rice (Os), and Arabidopsis (At). The yellow lines represent the collinear gene pairs between Lonicera macranthoides and tobacco, the red lines represent the collinear gene pairs between Lonicera macranthoides and Arabidopsis, the green lines represent the collinear gene pairs between Lonicera macranthoides and rice, and the blue lines represent the duplicated LmLHT genes.

FIGURE 5

Cis-acting element analysis in the promoter region of LmLHT genes. The numbers and colors in the box represent different elements.

FIGURE 6

Expression levels of LmLHT in selected tissues. L: leaf, R: root, S: stem, WF: white flower, YF: yellow flower. Expression levels of LmLHT in leaves were set to one. Data are mean ± SD (n = 3).

FIGURE 7

Expression levels of LmLHT under cold and drought stresses, seedlings under normal conditions were used as controls. Data are mean ± SD (n = 3).