Collagen has a unique SEC24 preference for efficient export from the endoplasmic reticulum

Procollagen requires COPII coat proteins for export from the endoplasmic reticulum (ER). SEC24 is the major component of the COPII proteins that selects cargo during COPII vesicle assembly. There are four paralogs (A to D) of SEC24 in mammals, which are classified into two subgroups. Pathological mutations in SEC24D cause osteogenesis imperfecta with craniofacial dysplasia in humans and sec24d mutant fish also recapitulate this phenotypes. Consistent with the skeletal phenotypes, the secretion of collagen was severely defective in mutant fish, emphasizing the importance of SEC24D in collagen secretion. However, SEC24D patient derived fibroblasts show only a mild secretion phenotype, suggesting tissue-specificity in the secretion process. To explore this possibility, we generated Sec24d knockout (KO) mice. Homozygous KO mice died prior to bone development. When we analyzed embryonic and extraembryonic tissues of mutant animals, we observed tissue-dependent defects of procollagen processing and ER export. The spacial patterns of these defects mirrored with SEC24B deficiency. By systematically knocking down the expression of Sec24 paralogs, we determined that, in addition to SEC24C and SEC24D, SEC24A and SEC24B also contribute to collagen secretion. In contrast, fibronectin 1 preferred either SEC24C or SEC24D. On the basis of our results, we propose that procollagen interacts with multiple SEC24 paralogs for efficient export from the ER, and that this is the basis for tissue-specific phenotypes resulting from SEC24 paralog deficiency

A Comparison of Two Soybean (Glycine max, L.) Lines for Flood Tolerance Mechanisms

Flooding can be defined as excess water in the root environment of land plants. This excess water can be injurious or lethal to plants due to blocking of oxygen transfer and other gases between root, soil, and atmosphere. Since waterlogging and flooding occur primarily at root-level, changes in environmental oxygen have effects on root biochemistry and metabolism that lead to physical changes in plant anatomy. Plants that can tolerate flooded soils demonstrate a myriad of responses. Physiological and molecular responses to flooding have been reported for soybean, a generally flood intolerant plant. Greenness (chlorophyll amounts) significantly decreased in flooded soybeans and total nitrogen content of flooded soybeans decreased significantly in roots and shoots. Photosynthesis rates reportedly are reduced significantly. Some soybean lines showed greater acclimation to flooding by avoidance of water loss by transcription (small leaf area) and increased transport of atmosphere O2 to roots via adventitious roots and aerenchyma tissue formation. A research project was developed to examine one flood tolerant and one flood intolerant soybean line for flood tolerance mechanisms. Specifically, whole-plant morphological changes, root tip DNA activity, and root nodule characteristics were observed under flooded and nonflooded conditions. Cytokinins, plant growth regulators produced mainly in root meristematic areas, were also examined as a possible key factor for flood tolerance. The results provided no absolute evidence for cytokinins and cytokinin production as the key to soybean flood tolerance. Rather, evidence indicated flood tolerant soybeans having the anatomical structure and metabolic pathways in place prior to flooding, resulting in vital resources being used for growth and development. Flood intolerant soybeans, responding to flood conditions, metabolically and morphologically changed, resulting in vital resources being diverted to flood survival

Collagen has a unique SEC24 preference for efficient export from the endoplasmic reticulum

SEC24 is mainly involved in cargo sorting during COPII vesicle assembly. There are four SEC24 paralogs (A–D) in vertebrates, which are classified into two subgroups (SEC24A/B and SEC24C/D). Pathological mutations in SEC24D cause osteogenesis imperfecta with craniofacial dysplasia in humans. sec24d mutant fish also recapitulate the phenotypes. Consistent with the skeletal phenotypes, the secretion of collagen was severely defective in mutant fish, emphasizing the importance of SEC24D in collagen secretion. However, SEC24D patient-derived fibroblasts show only a mild secretion phenotype, suggesting tissue-specificity in the secretion process. Using Sec24d KO mice and cultured cells, we show that SEC24A and SEC24B also contribute to endoplasmic reticulum (ER) export of procollagen. In contrast, fibronectin 1 requires either SEC24C or SEC24D for ER export. On the basis of our results, we propose that procollagen interacts with multiple SEC24 paralogs for efficient export from the ER, and that this is the basis for tissue-specific phenotypes resulting from SEC24 paralog deficiency.This is the published version of the following article: Lu, Chung‐Ling, Steven Ortmeier, Jon Brudvig, Tamara Moretti, Jacob Cain, Simeon A. Boyadjiev, Jill M. Weimer, and Jinoh Kim. "Collagen has a unique SEC24 preference for efficient export from the endoplasmic reticulum." Traffic 23, no. 1 (2022): 81-93. DOI: 10.1111/tra.12826. Copyright 2021 The Authors. Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0). Posted with permission