This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Saeed, M. Articles by Duke, S. H. Search for Related Content PubMed PubMed Citation Articles by Saeed, M. Articles by Duke, S. H. Agricola Articles by Saeed, M. Articles by Duke, S. H.

Metabolism and Enzymology

Amylases in Pea Tissues with Reduced Chloroplast Density and/or Function ¹

Department of Agronomy, University of Wisconsin, Madison, Wisconsin 53706-1597

Pea (Pisum sativum L.) tissues with reduced chloroplast density (e.g. petals and stems) or function (i.e. senescent leaves and leaves darkened for prolonged periods) were surveyed to determine whether tissues with genetically or environmentally reduced chloroplast density and/or function also have significantly different amylolytic enzyme activities and/or isoform patterns than leaf tissues with totally competent chloroplasts. Native PAGE followed by electrophoretically blotting through a starch or -limit dextrin containing gel and KI/I₂ staining revealed that the primary amylases in leaves, stems, petals, and roots were the primarily vacuolar -amylase (EC 3.2.1.2) and the primarily apoplastic -amylase (EC 3.2.1.1). Among tissues of light grown pea plants, petals contained the highest levels of total amylolytic (primarily -amylase) activity and considerably higher ratios of - to -amylase. In aerial tissues there was an inverse relationship between chlorophyll and starch concentration, and -amylase activity. In sections of petals and stems there was a pronounced inverse relationship between chlorophyll concentration and the activity of -amylase. Senescing leaves of pea, as determined by age, and protein and chlorophyll content, contained 3.8-fold (fresh weight basis) and 32-fold (protein basis) higher -amylase activity than fully mature leaves. Leaves maintained in darkness for 12 days displayed a 14-fold (fresh weight basis) increase in -amylase activity over those grown under continuous light. In senescence and prolonged darkness studies, the -amylase that was greatly increased in activity was the primarily apoplastic -amylase. These studies indicate that there is a pronounced inverse relationship between chloroplast function and levels of apoplastic -amylase activity and in some cases an inverse relationship between chloroplast density and/or function and vacuolar -amylase activity.