Allelic analysis of the maize amylose-extender locus suggests that independent genes encode starch-branching enzymes IIa and IIb

Dane K. Fisher, Ming Gao, Kyung Nam Kim, Charles D. Boyer, Mark J. Guiltinan

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51 Scopus citations

Abstract

Starch branching enzymes (SBE) catalyze the formation of α-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 S6e2b-hybridizing message expressed in endosperm, the ae gene also encodes the major Sbe2b-like transcript expressed in developing embryos and tassels.

Original languageEnglish (US)
Pages (from-to)611-619
Number of pages9
JournalPlant physiology
Volume110
Issue number2
DOIs
StatePublished - Feb 1996

All Science Journal Classification (ASJC) codes

  • Physiology
  • Genetics
  • Plant Science

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