College of Agronomy, Northwest A&F University, Yangling, Shaanxi, 712100, China.
J Appl Genet. 2013 May;54(2):135-45. doi: 10.1007/s13353-012-0132-y. Epub 2013 Jan 18.
Yellow seed is a desirable characteristic for the breeding of oilseed Brassica crops, but the manifestation of seed coat color is very intricate due to the involvement of various pigments, the main components of which are flavonols, proanthocyanidin (condensed tannin), and maybe some other phenolic relatives, like lignin and melanin. The focus of this review is to examine the genetics mechanism regarding the biosynthesis and regulation of these pigments in the seed coat of oilseed Brassica. This knowledge came largely from recent researches on the molecular mechanism of TRANSPARENT TESTA (tt) and similar mutations in the ancestry model plant of Brassica, Arabidopsis. Some key enzymes in the flavonoid (flavonols and proanthocyanidin) biosynthetic pathway have been characterized in tt mutants. Some orthologs to these TRANSPARENT TESTA genes have also been cloned in Brassica species. However, it is suggested that some alterative metabolism pathways, including lignin and melanin, might also be involved in seed color manifestation. Polyphenol oxidases, such as laccase, tyrosinase, or even peroxidase, participate in the oxidation step in proanthocyanidin, lignin, and melanin biosynthesis. Moreover, some researches also suggested that melanic pigment in black-seeded Brassica was several fold higher than in yellow-seeded Brassica. Although more experiments are required to evaluate the importance of lignin and melanin in seed coat browning, the current results suggest that the flavonols and proanthocyanidin are not the only roles affecting seed color.
黄色种子是培育油料作物芸薹属作物的理想特征，但由于涉及各种色素，种皮颜色的表现非常复杂，其主要成分是类黄酮、原花青素（缩合单宁），也许还有一些其他酚类物质，如木质素和黑色素。本文综述的重点是研究油料作物芸薹属种子种皮中这些色素生物合成和调控的遗传机制。这些知识主要来自于对模式植物拟南芥中 TRANSPARENT TESTA（tt）及其类似突变的分子机制的最新研究。在 tt 突变体中，类黄酮（类黄酮和原花青素）生物合成途径中的一些关键酶已被鉴定。在芸薹属物种中也克隆了一些与这些 TRANSPARENT TESTA 基因的同源物。然而，有人认为，一些替代性代谢途径，包括木质素和黑色素，也可能参与种子颜色的表现。多酚氧化酶，如漆酶、酪氨酸酶，甚至过氧化物酶，参与原花青素、木质素和黑色素生物合成中的氧化步骤。此外，一些研究还表明，黑籽芸薹属中黑色素的含量比黄籽芸薹属高几倍。尽管还需要更多的实验来评估木质素和黑色素在种皮变褐中的重要性，但目前的结果表明，类黄酮和原花青素并不是影响种子颜色的唯一因素。
