Rice prolamines are sequestered within the endoplasmic reticulum (ER) lumen even though they lack a lumenal retention signal. Immunochemical and biochemical data show that BiP, a protein that binds lumenal polypeptides, is localized on the surface of the aggregated prolamine protein bodies (PBs). BiP also forms complexes with nascent chains of prolamines in polyribosomes and with free prolamines with distinct adenosine triphosphate sensitivities. Thus, BiP retains prolamines in the lumen by facilitating their folding and assembly into PBs.
Summary• The function of calcium oxalate (CaOx) raphide crystal formation, and structural features related to regulation of crystal formation, were studied in Lemna minor fronds using physiological and microscopy techniques.• Specialized crystal-forming cells (crystal idioblasts) increased in number and size; CaOx, but not soluble oxalate, increased in response to increasing calcium in the growth medium. Size and number of idioblasts had a distinct upper limit.• The CaOx crystals are formed in membranous 'chambers' and connected in rows by parallel membrane sheets, both forming de novo in the vacuole. The chambers, but not parallel membranes, had calcium associated with them. A calcium-binding matrix protein was associated with idioblast vacuoles and crystal formation.• Lemna crystal idioblasts function as calcium-inducible, specialized high-capacity but saturable sinks for bulk regulation of calcium, and crystal deposition is a highly controlled process requiring intravacuolar membrane systems and calcium-binding organic matrix materials.
The formation of calcium (Ca) oxalate crystals is considered to be a high-capacity mechanism for regulating Ca in many plants. Ca oxalate precipitation is not a stochastic process, suggesting the involvement of specific biochemical and cellular mechanisms. Microautoradiography of water lettuce (Pistia stratiotes) tissue exposed to 3 H-glutamate showed incorporation into developing crystals, indicating potential acidic proteins associated with the crystals. Dissolution of crystals leaves behind a crystal-shaped matrix "ghost" that is capable of precipitation of Ca oxalate in the original crystal morphology. To assess whether this matrix has a protein component, purified crystals were isolated and analyzed for internal protein.Polyacrylamide gel electrophoresis revealed the presence of one major polypeptide of about 55 kD and two minor species of 60 and 63 kD. Amino acid analysis indicates the matrix protein is relatively high in acidic amino acids, a feature consistent with its solubility in formic acid but not at neutral pH.45 Ca-binding assays demonstrated the matrix protein has a strong affinity for Ca. Immunocytochemical localization using antibody raised to the isolated protein showed that the matrix protein is specific to crystal-forming cells. Within the vacuole, the surface and internal structures of two morphologically distinct Ca oxalate crystals, raphide and druse, were labeled by the antimatrix protein serum, as were the surfaces of isolated crystals. These results demonstrate that a specific Ca-binding protein exists as an integral component of Ca oxalate crystals, which holds important implications with respect to regulation of crystal formation.Many plants produce calcium (Ca) oxalate as crystalline deposits (Arnott and Pautard, 1970; Gallaher, 1975; Franceschi and Horner, 1980; Horner and Wagner, 1995; Webb, 1999; Nakata, 2003), which can account for greater than 85% of the dry weight of some plant organs. The formation of Ca oxalate is an essential process in many species, and more than 90% of tissue Ca can be tied up as this compound (Gallaher et al., 1975; Gallaher and Jones, 1976). Ca oxalate crystals often occur within the vacuole of crystal idioblasts (Foster, 1956), specialized cells that generally encompass less than 1% to 2% of the total cells of the Ca-accumulating tissue. Because Ca oxalate formation is the end result of a mechanism for controlling Ca at the tissue and organ levels in the plant (Zindler-Frank, 1975; Borchert, 1985; Franceschi, 1989 Franceschi, , 2001 DeSilva et al., 1996; Kuo-Huang and Zindler-Frank, 1998; Pennisi and McConnell, 2001; Zindler-Frank et al., 2001; Volk et al., 2002), cells producing the crystals are considered to be highcapacity Ca sinks. Because crystal idioblasts perform a unique complex function of importance to the general physiology of the plant, and they commonly occur as single cells scattered among other tissues, we have referred to them as single-celled organs (Kostman and Franceschi, 2000).Large amounts of Ca oxalate crystals can be formed...
The objective of this study was to examine the associations of red meat, poultry, and egg consumption with the risk of hypertension (HTN). The electronic databases of PubMed, Web of Science, and Embase were searched up to August 2017, for prospective cohort studies on the associations between red meat, poultry, or egg consumption with the risk of HTN. The pooled relative risk (RR) of HTN for the highest vs. lowest category of red meat, poultry, and egg consumption as well as their corresponding 95% confidence interval (CI) were calculated. A total of eight articles made up of 10 prospective cohort studies, which involved 351,819 participants and 5000 HTN cases, were included in this meta-analysis. Specifically, nine studies were related to red meat consumption, and the overall multi-variable adjusted RR showed a positive association between red meat consumption and the risk of HTN (RR = 1.22, 95% CI: 1.11-1.35; P < 0.001). In the subgroup analysis that consisted of five studies, both processed (RR = 1.12, 95% CI: 1.02-1.23; P = 0.02) and unprocessed (RR = 1.19, 95% CI: 1.04-1.36; P = 0.01) red meat were associated with a higher risk of HTN. In addition, in the six studies related to poultry consumption, the overall multi-variable adjusted RR demonstrated that poultry consumption was also associated with a higher risk of HTN (RR = 1.15, 95% CI: 1.03-1.28; P = 0.015). Moreover, three of the studies that were included were related to egg consumption, and the overall multi-variable-adjusted RR showed that egg consumption was associated with a lower risk of HTN (RR = 0.79, 95% CI: 0.68-0.91; P = 0.001). The existing evidence suggested that red meat (both processed and unprocessed) and poultry consumption were associated with a higher risk of HTN, while egg consumption was associated with a lower risk of HTN. Owing to the limited number of studies, more well-designed prospective cohort studies are needed to further elaborate the issues examined in this study.
Abstract. The classical induction of Crassulacean acid metabolism (CAM) in Mesembryanthemum crystallinum
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