Molecular Characterization and Expression Profiling of L. Cystatin Genes Reveal High Evolutionary Conservation and Functional Divergence in Response to Abiotic Stress.

Cystatin is a class of proteins mainly involved in cysteine protease inhibition and plant growth and development, as well as tolerance under various abiotic stresses. In this study, we performed the first comprehensive analysis of the molecular characterization and expression profiling in response to various abiotic stresses of the cystatin gene family in , a novel model plant for species with huge genomes. Comprehensive searches of the genome database identified 25 () genes that are distributed unevenly on chromosomes; of these, nine and two were involved in tandem and segmental duplication events, respectively. All genes had similar exon/intron structural organization, with three conserved motifs similar to those from other plant species, indicating their high evolutionary conservation. Expression profiling of 10 typical genes revealed ubiquitous expression in different organs at varying expression levels. gene expression in seedling leaves was particularly highly induced by various abiotic stresses, including the plant hormone abscisic acid and various environmental cues (cold, HO, CdCl, salt, and drought). Interestingly, most genes were significantly upregulated under multiple abiotic stresses, including under all stresses, and under five stresses, and , and under four stresses. The putative metabolic pathways of cytastin genes in response to various abiotic stresses mainly involve the aberrant protein degradation pathway and reactive oxygen species (ROS)-triggered programmed cell death signaling pathways. These observations provide a better understanding of the structural and functional characteristics of the plant cystatin gene family.