Hong, H. T. | bioRxiv Science

bioRxiv2022

PROFILING AND QUANTIFICATION OF ANTHOCYANINS IN NOVEL PURPLE-PERICARP SWEETCORN AND PURPLE-PERICARP MAIZE

Anthocyanins, secondary metabolites of pigmented corns consisting of cyanidin-, pelargonidin- and peonidin-based glucoside. While cyanidin-peonidin types are responsible for purple-pigmentation, pelargonidin type is responsible for red-pigmentation. This study examined anthocyanin concentrations in a novel purple-pericarp shrunken2 sweetcorn Tim lines in comparison to the parental purple-pericarp Costa Rica maize and white sweetcorn Tims-white lines. The study found similar concentrations of anthocyanin in both Tim1 and the Costa Rica, at sweetcorn eating stage, whereas Tims-white has no detectable anthocyanin. Total anthocyanins found in the Costa Rica and Tim1, Tim2, Tim4 and Tim5 lines were 255.79, 253.03, 238.10, 198.66, and 221.36 mg/100 g FW (fresh weight), respectively. In all the developed purple-sweetcorn Tim lines along with the purple maize parent, the cyanidin-peonidin (purple) proportion of total anthocyanin was 78-93%, as the predominant anthocyanin pigment. The anthocyanin concentration in Tim1 at eating stage was significantly much higher than currently exists with other coloured fruits.

biochemistry↗

bioRxiv2022

BREAKING THE TIGHT GENETIC LINKAGE BETWEEN THE a1 AND sh2 GENES LED TO THE DEVELOPMENT OF ANTHOCYANIN-RICH PURPLE-PERICARP SUPER-SWEETCORN

The existence of purple-pericarp super-sweetcorn based on the most common supersweet mutation, shrunken2 (sh2), has not been previously reported, partly due to its extremely tight genetic linkage to a non-functional anthocyanin biosynthesis gene, anthocyaninless1 (a1). Generally, both aleurone- and pericarp-pigmented purple corn is starchy, the latter of which contains significantly higher anthocyanin compared to the former. The development of purple-pericarp super-sweetcorn is dependent on breaking the a1-sh2 tight genetic linkage, which occurs at a very low frequency of <1 in 1000 meiotic crossovers. Here, to develop purple-pericarp super-sweetcorn, an initial cross between a male purple-pericarp maize (purple-round seed), Costa Rica (A1Sh2.A1Sh2) and a female white shrunken2 super-sweetcorn (white-shrunken seed), Tims-white (a1sh2.a1sh2), was conducted. Subsequent self-pollination based on purple-pericarp-shrunken kernels identified a small frequency (0.08%) of initial heterozygous F3 segregants (A1a1.sh2sh2) producing a fully sh2 cob with a purple-pericarp phenotype, enabled by breaking the close genetic linkage between the a1 and sh2 genes. Resulting rounds of self-pollination generated a F6 homozygous purple-pericarp super-sweetcorn (A1A1.sh2sh2) line, Tim1. Genome sequencing revealed a recombination break between the a1 and yz1 genes of the a1-yz1-x1-sh2 multigenic interval, with the sequence pattern of Tim1 similar to the Costa Rica parent, and after the linkage break, similar to the Tims-white parent. The novel purple-pericarp super-sweetcorn produced a similar concentration of anthocyanin and sugar as in its purple-pericarp maize and white super-sweetcorn parents, respectively, potentially adding a broader range of health benefits than currently exists with standard yellow/white sweetcorn.

plant biology↗