title: Comprehensive analysis of cystatin family genes suggests their putative functions in sexual reproduction, embryogenesis, and seed formation.
abstract: Cystatins are tightly bound and reversible inhibitors of cysteine proteases in C1A and C13 peptidase families, which have been identified in several species and shown to function in vegetative development and response to biotic/abiotic stresses in plants. Recent work revealed their critical role in regulating programmed cell death during embryogenesis in tobacco and suggested their more comprehensive roles in the process of sexual plant reproduction, although little is known about cystatin family genes in the processes. Here, 10 cystatin family genes in Nicotiana tabacum were identified using an expressed sequence tag (EST)-based gene clone strategy. Analysis of their biochemical properties showed that nine of them have the potency to inhibit the activities of both commercial cathepsin L-like proteases and extracted cysteine proteases from seeds, but with different K i values depending on the types of proteases and the developmental stages of the seed tested. This suggests that cystatin-dependent cathepsin L-like proteolytic pathways are probably important for early seed development. Comprehensive expression profile analysis revealed that cystatin family genes showed manifold variations in their transcription levels in different plant cell types, including the sperm, egg, and zygote, especially in the embryo and seed at different developmental stages. More interestingly, intracellular localization analysis of each cystatin revealed that most members of cystatin families are recognized as secretory proteins with signal peptides that direct them to the endoplasmic reticulum. These results suggest their widespread roles in cell fate determination and cell-cell communication in the process of sexual reproduction, especially in gamete and embryo development, as well as in seed formation.
authors.affiliation: Department of Cell and Developmental Biology, College of Life Sciences, State Key Laboratory of Plant Hybrid rice, Wuhan University, Wuhan 430072, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhao
authors.affiliation: Department of Cell and Developmental Biology, College of Life Sciences, State Key Laboratory of Plant Hybrid rice, Wuhan University, Wuhan 430072, China.
authors.forename: Xue-mei
authors.initials: XM
authors.lastname: Zhou
authors.affiliation: Molecular Genetics Key Laboratory of China Tobacco, Guizhou Academy of Tobacco Science, Guiyang 550081, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Zou
authors.affiliation: Department of Cell and Developmental Biology, College of Life Sciences, State Key Laboratory of Plant Hybrid rice, Wuhan University, Wuhan 430072, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden of the Chinese Academy of Sciences, Wuhan 430074, China.
authors.forename: Lu
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Cell and Developmental Biology, College of Life Sciences, State Key Laboratory of Plant Hybrid rice, Wuhan University, Wuhan 430072, China.
authors.forename: Xiong-bo
authors.initials: XB
authors.lastname: Peng
authors.affiliation: Department of Cell and Developmental Biology, College of Life Sciences, State Key Laboratory of Plant Hybrid rice, Wuhan University, Wuhan 430072, China mxsun@whu.edu.cn.
authors.forename: Meng-xiang
authors.initials: MX
authors.lastname: Sun
mesh_terms: D000595:Amino Acid Sequence; D015891:Cystatins / Q000235:genetics* / Q000378:metabolism; D020224:Expressed Sequence Tags; D056130:Gametogenesis, Plant; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D012098:Reproduction; D012639:Seeds / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D016415:Sequence Alignment; D014026:Nicotiana / Q000235:genetics / Q000254:growth & development / Q000502:physiology*
chemical_list: D015891:Cystatins; D010940:Plant Proteins
keywords: Cathepsin L-like proteases; cystatin; embryogenesis; seed development; sexual reproduction; tobacco.