Authors:N. Li, Y. Zong, B.L. Liu, W.J. Chen, and B. Zhang
Purple pericarp is an interesting and useful trait in Triticum aestivum, but the molecular mechanism behind this phenotype remains unclear. The allelic variation in the MYB transcriptors is associated with the phenotype of pigmented organs in many plants. In this study, a MYB transcription factor gene, TaMYB3, was isolated using homology-based cloning and a differentially expressed gene mining approach, to verify the function of the MYB transcriptor in the purple pericarp. The coding sequence of TaMYB3 in cultivar Gy115 was the same as that in cultivar Opata. TaMYB3 was localized to FL0.62–0.95 on chromosome 4BL. The TaMYB3 protein contains DNA-binding and transcription-activation domains, and clustered on a phylogenetic tree with the MYB proteins that regulates anthocyanin and proanthocyanin biosynthesis. TaMYB3 localized in the nuclei of Arabidopsis thaliana and wheat protoplasts after it was transiently expressed with PEG transformation. TaMYB3 induced anthocyanin synthesis in the pericarp cells of Opata in the dark in collaboration with the basic helix–loop–helix protein ZmR, which is also the function of ZmC1. However, TaMYB3 alone did not induce anthocyanin biosynthesis in the pericarp cells of the white grain wheat cultivar Opata in the light after bombardment, whereas the single protein ZmR did. Light increased the expression of TaMYB3 in the pericarp of Gy115 and Opata, but only induced anthocyanin biosynthesis in the grains of Gy115. Our results extend our understanding of the molecular mechanism of the purple pericarp trait in T. aestivum.
Anthocyanins are natural antioxidants able to scavenge free radicals, which appear in plant cells under various environmental stresses. In wheat, anthocyanin pigments can be synthesized in vegetative and reproductive organs. The objective of the current study was to estimate the significance of these substances for wheat seedlings protection under irradiation stress (after treatment of dry seeds with moderate doses of gamma-irradiation, 50, 100 and 200 Gy). For this goal a set of near-isogenic lines (8 NILs) carrying different combinations of the Pp (purple pericarp) and Rc (red coleoptile) alleles were used. The effect of gammairradiation on the growth parameters and anthocyanin content in coleoptiles was studied at the 4th day after germination. The germination rate was not affected, while roots’ and shoots’ lengths and fresh weights as well as root number decreased significantly under irradiation treatment. The effect was deeper under higher doses. Irradiation treatment also induced change of root morphology (‘hairy roots’). The effect of treatment on coleoptile anthocyanin content depended on allelic combination at the Rc loci. At the presence of ‘weak’ Rc-A1 allele anthocyanin content decreased, while it did not change in lines with Rc-A1 + Rc-D1 combination (NILs with intensively colored coleoptiles). Factors ‘pericarp color’ and ‘coleoptile color’ influenced vigor of the seedlings under 50 Gy, whereas under higher doses (100 and 200 Gy) these factors did not contribute to growth parameters changes. Statistically significant positive effect of anthocyanins synthesized in coleoptile (in the presence of Rc-A1 + Rc-D1 dominant alleles) on root growth of seedling germinated from 50 Gy-treated seeds was observed.