Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.25.1 (proteasome)
 28,817 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To elucidate the regulatory mechanisms of carotenogenesis in Japanese apricot (Prunus mume Siebold & Zucc.), the relationships between carotenoid accumulation and the expression of the carotenogenic genes, phytoene synthase (PmPSY-1), phytoene desaturase (PmPDS), zeta-carotene desaturase (PmZDS), lycopene beta-cyclase (PmLCYb), lycopene epsilon-cyclase (PmLCYe), beta-carotene hydroxylase (PmHYb), and zeaxanthin epoxidase (PmZEP), were analyzed in two cultivars with different ripening traits, 'Orihime' and 'Nanko.' In 'Orihime' fruits, large amounts of carotenoids accumulated on the tree, concomitant with the induction of PmPSY-1 and the downstream carotenogenic genes PmLCYb, PmHYb, and PmZEP. In 'Nanko' fruits, carotenoids accumulated mainly after harvest, correlating with an appreciable induction of PmPSY-1 expression, but the downstream genes were not notably induced, which may explain the lower total carotenoid content in 'Nanko' than in 'Orihime.' In both cultivars, a decrease in PmLCYe expression and increased or constant PmLCYb expression could cause the metabolic shift from beta,epsilon-carotenoid synthesis to beta,beta-carotenoid synthesis that occurs as ripening approaches. Next, the effects of ethylene on the expression of PmPSY-1 and carotenoid accumulation were investigated in 'Nanko' fruits treated with propylene or 1-methylcyclopropene (1-MCP). Propylene treatment induced both ethylene production and carotenoid accumulation. PmPSY-1 was constitutively expressed, but propylene treatment accelerated its induction. 1-MCP treatment caused a slight inhibition of carotenoid accumulation along with the repression, although not complete, of PmPSY-1. Collectively, although PmPSY-1 expression was not exclusively regulated by ethylene, both the notable induction of PmPSY-1 accelerated by ethylene and the subsequent induction of the downstream carotenogenic genes, especially PmLCYb, could be necessary for the massive carotenoid accumulation that occurs during ripening. Furthermore, the switch from PmLCYe expression to PmLCYb expression could cause beta,beta-carotenoid accumulation in both Japanese apricot cultivars.
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PMID:Carotenoid accumulation in Japanese apricot (Prunus mume Siebold & Zucc.): molecular analysis of carotenogenic gene expression and ethylene regulation. 1739 80

The promoter of phytoene synthase, the first specific enzyme of carotenoid biosynthesis, shows two main regulatory regions: a G-box-containing region located near the TATA box, and a TATA box distal region containing the cis-acting element ATCTA, which mediates strong basal promoter activity. This second element was also present in the promoter of phytoene desaturase, the next step of the carotenoid pathway, suggesting a common regulatory mechanism. In this work, we demonstrate that AtRAP2.2, a member of the APETALA2 (AP2)/ethylene-responsive element-binding protein transcription factor family, binds to the ATCTA element. In Arabidopsis (Arabidopsis thaliana) leaves, AtRAP2.2 transcript and protein levels were tightly controlled as indicated by unchanged transcript and protein levels in T-DNA insertion mutants in the AtRAP2.2 promoter and 5' untranslated region and the lack of change in AtRAP2.2 protein levels in lines strongly overexpressing the AtRAP2.2 transcript. Homozygous loss-of-function mutants could not be obtained for the AtRAP2.2 5' untranslated region T-DNA insertion line indicating a lethal phenotype. In AtRAP2.2 overexpression lines, modest changes in phytoene synthase and phytoene desaturase transcripts were only observed in root-derived calli, which consequently showed a reduction in carotenoid content. The RING finger protein SEVEN IN ABSENTIA OF ARABIDOPSIS2 (SINAT2) was identified as an AtRAP2.2 interaction partner using a two-hybrid approach. The structure of SINAT2 and related proteins of Arabidopsis show homology to the SEVEN IN ABSENTIA protein of Drosophila that is involved in proteasome-mediated regulation in a variety of developmental processes. The action of SINAT2 may explain the recalcitrance of AtRAP2.2 protein levels to change by altering AtRAP2.2 transcription.
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PMID:Transcription factor RAP2.2 and its interacting partner SINAT2: stable elements in the carotenogenesis of Arabidopsis leaves. 1787 90