Molecular Basis of the Waxy Endosperm Starch Phenotype in Broomcorn Millet (Panicum miliaceum L.)

摘要: Waxy varieties of the tetraploid cereal broomcorn millet (Panicum miliaceum L.) have endosperm starch granules lacking detectable amylose. This study investigated basis this phenotype using molecular and biochemical methods. Iodine staining in 72 plants from 38 landrace accessions found 58 nonwaxy 14 waxy plants. All types were Chinese Korean accessions, a distribution similar to that other cereals. Granule-bound synthase I (GBSSI) protein was present both individuals, but had little or no granule-bound activity compared with wild types. Sequencing GBSSI (Waxy) gene showed is two different forms (L S) P. miliaceum, which probably represent homeologues derived distinct diploid ancestors. Protein products these are granules. We identified three polymorphisms exon sequence coding for mature peptides. A 15-bp deletion has occurred S type GBSSI, resulting loss five amino acids glucosyl transferase domain 1 (GTD1). The second (L) shows polymorphisms. One insertion an adenine residue causes reading frameshift, cysteine-tyrosine acid polymorphism. These mutations appear parallel ancestral allele, GBSSI-L alleles total. Five six possible genotype combinations L observed. GBSSI-S activity, there 100% correspondence between phenotype. frameshift mutation results L-type isoform tyrosine nonfunctional. function may result substitution cysteine, although it could not be determined whether cysteine represents functional type. first characterization occur combination functionally polyploid species give fully