The glume is an organ of the maize spikelet and plays important roles in anther and kernel development. Vestigial glume1 (Vg1) is a classic mutant associated with ligule and glume development. Here we report the phenotypic characterization, fine mapping, and candidate gene analysis of the Vg1 mutant. Vg1 is a semi-dominant and pleiotropic gene, and also affects plant height, ear height, and tassel length. Vg1 ligule degeneration begins at the first leaf, and the Vg1 tassel and ear can be distinguished from those of wild-type plants when their lengths reach respectively 55 mm and 51 mm. Using a BC₃ mapping population of 11,445 plants, we delimited the Vg1 functional site to an interval of 7.4 kb, flanked by the markers InDelLM and CRM6. A putative cyclopropane fatty-acid synthase gene (ZmCPA-FAS1) was hypothesized to underlie the mutant phenotype. We detected a Helitron insertion in the sixth intron of ZmCPA-FAS1. Its presence caused abnormal alternative splicing of ZmCPA-FAS1 that conferred new characteristics on the Vg1 mutant. These findings are a basis for further discovery of the molecular mechanism underlying glume development and a potential guide for maize breeding of small-glume varieties, especially sweet corn breeding.

The maize mutant gene Vestigial glume 1 (Vg1) has been fine-mapped to a narrow region by map-based cloning and the candidate gene for Vg1 spanned 19.5 kb. Here we report Vg1 genomic fosmid library construction and screening. The fosmid library of Vg1 consisted of 574,000 clones with an average insert size of 36.4 kb, representing 7.9-fold coverage of the maize genome. Fosmid stability assays indicated that clones were stable during propagation in the fosmid system. Using Vg1 candidate gene-specific primers, a positive clone was successfully identified. This discovery will pave the way for identifying the function of Vg1 in maize development.

ZAG2 has been identified as a maternally expressed imprinted gene in maize endosperm. Our study revealed that paternally inherited ZAG2 alleles were imprinted in maize endosperm and embryo at 14 days after pollination (DAP), and consistently imprinted in endosperm at 10, 12, 16, 18, 20, 22, 24, 26, and 28 DAP in reciprocal crosses between B73 and Mo17. ZAG2 alleles were also imprinted in reciprocal crosses between Zheng 58 and Chang 7-2 and between Huang C and 178. ZAG2 alleles exhibited differential imprinting in hybrids of 178 × Huang C and B73 × Mo17, while in other hybrids ZAG2 alleles exhibited binary imprinting. The tissue-specific expression pattern of ZAG2 showed that ZAG2 was expressed at a high level in immature ears, suggesting that ZAG2 plays important roles in not only kernel but ear development.