Allelic Analysis of the Maize amylose-extender Locus Suggests That Independent Genes Encode Starch-Branching Enzymes IIa and IIb.
AUTOR(ES)
Fisher, D. K.
RESUMO
Starch branching enzymes (SBE) catalyze the formation of [alpha]-1,6-glucan linkages in the biosynthesis of starch. Three distinct SBE isoforms have been identified in maize (Zea mays L.) endosperm, SBEI, IIa, and IIb. Independent genes have been identified that encode maize SBEI and IIb; however, it has remained controversial as to whether SBEIIa and IIb result from posttranscriptional processes acting on the product of a single gene or whether they are encoded by separate genes. To investigate this question, we analyzed 16 isogenic lines carrying independent alleles of the maize amylose-extender (ae) locus, the structural gene for SBEIIb. We show that 22 d after pollination ae-B1 endosperm expressed little Sbe2b (ae)-hybridizing transcript, and as expected, ae-B1 endosperm also lacked detectable SBEIIb enzymatic activity. Significantly, we show that ae-B1 endosperm contained SBEIIa enzymatic activity, strongly supporting the hypothesis that endosperm SBEIIa and IIb are encoded by separate genes. Furthermore, we show that in addition to encoding the predominant Sbe2b-hybridizing message expressed in endosperm, the ae gene also encodes the major Sbe2b-like transcript expressed in developing embryos and tassels.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=157757Documentos Relacionados
- Independent genetic control of maize starch-branching enzymes IIa and IIb. Isolation and characterization of a Sbe2a cDNA.
- The Two Genes Encoding Starch-Branching Enzymes IIa and IIb Are Differentially Expressed in Barley1
- Maize Starch-Branching Enzyme Isoforms and Amylopectin Structure. In the Absence of Starch-Branching Enzyme IIb, the Further Absence of Starch-Branching Enzyme Ia Leads to Increased Branching1
- Genetic Fine Structure Analysis of the AMYLOSE-EXTENDER Locus in ZEA MAYS L
- Biochemical and Genetic Analysis of the Effects of Amylose-Extender Mutation in Rice Endosperm