Fine Mapping and Candidate Gene Analysis of Maize (Zea mays) Sex Determination Gene tasselseed10
ZHU Si-Ying*, ZHU Ting-Ting*, LI Ting, DENG Ping, XIANG Xiao-Qin, WANG Jiu-Guang, WANG Guo-Qiang, LIU Chao-Xian**
Maize Research Institute/ Engineering Research Center of South Upland Agriculture, Ministry of Education/ Chongqing Key Laboratory of Crop Molecular Improvement, Southwest University, Beibei 400715; China
Abstract：Maize (Zea mays) is an important model plant to decipher the molecular mechanism of sex determination. The research on sex determination of tassel and ear is of great significance to improve the inflorescence architecture and increase yield. In this study, a maize sex determination mutant tasselseed10 (ts10) that could produce kernel on tassel was identified by treating B73 pollen with ethyl methane sulfonate (EMS). In fields, the vegetative growth of the ts10 was normal. When tassels emerged, the spikelets on middle and upper of main spikes and branches showed sex reversal, which could produce a large quantity of silks. While the apical spikelets could shed pollens normally. Phenotype observation under scanning electron microscope indicated when the male inflorescence meristem of ts10 was about 12 mm long, the florets produced feminized structure. Using map-based cloning strategy, the ts10 gene was narrowed down to a region of about 600 kb between the SSR markers PL4 and PR5 on Chr.1, which harbored 7 annotated genes. Sequencing analysis revealed that only the myelocytomatosis 7 (ZmMyc7) produced a mutation in which the 1 594th base G was substituted by base a resulting in the 532nd amino acid glutamic acid substituted by lysine. Further analysis suggested the mutation was located at the conserved domain HLH of ZmMyc7. Expression analysis showed that ts10 was expressed in root, stem, leaf, immature tassel, immature ear and kernel, among which the expression level in ear was the highest, followed by tassel; in addition, except for leaf, there was no significant difference in expression level of ZmMyc7 between ts10 and normal plants in root, stem, immature tassel, immature ear, embryo and endosperm. The subcellular localization results showed ZmMyc7 functions in nucleus. This study provides further theoretical support and genetic resources for enriching the molecular mechanism of sex determination in maize.
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