{"title":"Ribosomes and polyribosomes in Brassica pekinensis","authors":"M.F. Clark, R.E.F. Matthews, R.K. Ralph","doi":"10.1016/0926-6550(64)90253-1","DOIUrl":null,"url":null,"abstract":"<div><p>Leaves of <em>Brassica pekinensis</em> plants contain 83-S ribosomes which occur free in the cytoplasm rather than in chloroplasts. A 68-S class of ribosomes present in 20–35% the amount of the 83-S, occurs largely if not entirely in chloroplasts. Both classes may occur as polyribosomal aggregates which can be temporarily preserved in leaf extracts using polyvinyl sulphate as a nuclease inhibitor. The major environmental influence on polyribosome levels in leaves is a diurnal cycle in which light is the predominant factor. Polyribosomes decrease in amount during the night and reach their lowest level before dawn. 2 or 3 h after sunrise 80–90% of the 83-S ribosomes may be in polyribosomes. If the natural dark period is extended for 2–3 h no polyribosomes can be detected. When such plants are exposed to sunlight a rise in polyribosomes and a drop in 83-S ribosomes can be detected within 4 min. This light-dependent increase in polyribosomes appears to be associated, at least in part, with the synthesis of new RNA.</p></div>","PeriodicalId":100173,"journal":{"name":"Biochimica et Biophysica Acta (BBA) - Specialized Section on Nucleic Acids and Related Subjects","volume":"91 2","pages":"Pages 289-304"},"PeriodicalIF":0.0000,"publicationDate":"1964-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0926-6550(64)90253-1","citationCount":"88","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Biochimica et Biophysica Acta (BBA) - Specialized Section on Nucleic Acids and Related Subjects","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/0926655064902531","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 88
Abstract
Leaves of Brassica pekinensis plants contain 83-S ribosomes which occur free in the cytoplasm rather than in chloroplasts. A 68-S class of ribosomes present in 20–35% the amount of the 83-S, occurs largely if not entirely in chloroplasts. Both classes may occur as polyribosomal aggregates which can be temporarily preserved in leaf extracts using polyvinyl sulphate as a nuclease inhibitor. The major environmental influence on polyribosome levels in leaves is a diurnal cycle in which light is the predominant factor. Polyribosomes decrease in amount during the night and reach their lowest level before dawn. 2 or 3 h after sunrise 80–90% of the 83-S ribosomes may be in polyribosomes. If the natural dark period is extended for 2–3 h no polyribosomes can be detected. When such plants are exposed to sunlight a rise in polyribosomes and a drop in 83-S ribosomes can be detected within 4 min. This light-dependent increase in polyribosomes appears to be associated, at least in part, with the synthesis of new RNA.