title: Irregular xylem 7 (IRX7) is required for anchoring seed coat mucilage in Arabidopsis.
abstract: Large quantities of mucilage are synthesized in seed coat epidermis cells during seed coat differentiation. This process is an ideal model system for the study of plant cell wall biosynthesis and modifications. In this study, we show that mutation in Irregular Xylem 7 (IRX7) results in a defect in mucilage adherence due to reduced xylan biosynthesis. IRX7 was expressed in the seeds from 4 days post-anthesis (DPA) to 13 DPA, with the peak of expression at 13 DPA. The seed coat epidermis cells of irx7 displayed no aberrant morphology during differentiation, and these cells synthesized and deposited the same amount of mucilage as did wild type (WT) cells. However, the distribution of the water-soluble vs. adherent mucilage layers was significantly altered in irx7 compared to the WT. Both the amount of xylose and the extent of glycosyl linkages of xylan was dramatically decreased in irx7 water-soluble and adherent mucilage compared to the WT. The polymeric structure of water-soluble mucilage was altered in irx7, with a total loss of the higher molecular weight polymer components present in the WT. Correspondingly, whole-seed immunolabeling assays and dot-immunoassays of extracted mucilage indicated dramatic changes in rhamnogalacturonan I (RG I) and xylan epitopes in irx7 mucilage. Furthermore, the crystalline cellulose content was significantly reduced in irx7 mucilage. Taken together, these results indicate that xylan synthesized by IRX7 plays an essential role in maintaining the adhesive property of seed coat mucilage, and its structural role is potentially implemented through its interaction with cellulose.
authors.affiliation: Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, People's Republic of China.
authors.forename: Ruibo
authors.initials: R
authors.lastname: Hu
authors.affiliation: Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, People's Republic of China.
authors.forename: Junling
authors.initials: J
authors.lastname: Li
authors.affiliation: Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, People's Republic of China.
authors.forename: Xuanwen
authors.initials: X
authors.lastname: Yang
authors.affiliation: Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, People's Republic of China.
authors.forename: Xun
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, People's Republic of China.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Wang
authors.affiliation: Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, People's Republic of China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Tang
authors.affiliation: Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, People's Republic of China.
authors.forename: Guo
authors.initials: G
authors.lastname: He
authors.affiliation: Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, People's Republic of China. zhougk@qibebt.ac.cn.
authors.forename: Gongke
authors.initials: G
authors.lastname: Zhou
authors.affiliation: Tobacco Research Institute of Chinese Academy of Agricultural Sciences, Qingdao, Qingdao, 266101, People's Republic of China. kongyingzhen@caas.cn.
authors.forename: Yingzhen
authors.initials: Y
authors.lastname: Kong
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005964:Glucosyltransferases / Q000378:metabolism*; D010368:Pectins / Q000378:metabolism; D012639:Seeds / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C042491:rhamnogalacturonan I; D010368:Pectins; D002482:Cellulose; D005964:Glucosyltransferases
keywords: Arabidopsis; Crystalline cellulose; Irregular Xylem 7; Mucilage; Xylan