Computational Molecular Biology 2025, Vol.15, No.2, 65-74 http://bioscipublisher.com/index.php/cmb 66 2 Genetic Basis of Flower Pigmentation 2.1 Key pigments and their roles in flower color Anthocyanins, as a water-soluble pigment, are quite common in plants, and many colors such as red, purple, or blue are due to them. For example, in the case of Brassica napus, whether it is flowers, leaves, or stems, color cannot be formed without these substances. However, you may not know that these colors are not only for beauty, but also help plants cope with environmental pressure. Whether it is extreme weather or when there are pests and diseases, they have a certain defensive effect (Jiang, 2024). In B. napus, anthocyanin accumulation is not the the final say of one or two genes. Both structural genes and regulatory genes will participate, especially transcription factors such as MYB, which are particularly critical in the synthesis process. Carotenoids are also a common type of pigment, such as often making flowers appear yellow, orange or red. Rapeseed like B. napus mainly contains lutein and zeaxanthin in its yellow petals. Interestingly, some mutations can cause petals to have different colors-for instance, if the genes BnaA09.ZEP and BnaC09.ZEP are missing, even orange petals may appear. In addition to coloring, carotenoids are actually quite beneficial to the health of the plants themselves and their environmental resistance. Also, you may have heard of betaine, which comes from tyrosine and can form red and yellow colors in some plants, but it is generally not seen in B. napus. In fact, rape mainly relies on anthocyanins and carotenoids to present its color, and these two components play a more significant role in color formation (Grotewold, 2006). 2.2 Overview of biosynthetic pathways In B.napus, the synthesis of anthocyanins is not achieved in one step. It requires the conversion of several enzymes step by step-such as Chalketone synthase (CHS), chalketone isomerase (CHI), and anthocyanin synthase (ANS), etc. They basically start with phenylalanine and gradually synthesize anthocyanins. However, these enzymes alone are not enough; in many cases, the expression of regulatory genes also needs to be examined. Genes like BnaA07.PAP2 and BnaTT8, once activated, can make those enzyme genes expressed more strongly, and anthocyanins accumulate more in the petals. In fact, the entire synthetic pathway is quite delicate and is usually regulated jointly by transcription factors such as MYB, bHLH, and WD40. They form a complex and jointly control the on and off of biosynthetic genes (Yan et al., 2021). In B. napus, the synthesis of carotenoids actually relies heavily on genes like BnaA09.ZEP and BnaC09.ZEP, which encode zeaxanthin cyclooxygenase. Generally, if these genes are mutated or missing, the composition of carotenoids will be significantly different, and the color will also change accordingly. For example, if there is a problem with the BnaA09.ZEP and BnaC09.ZEP genes, the content of lutein will increase, while the amount of zeaxanthin in maize will decrease, and eventually the petals may turn from the common yellow to orange. Not only that, but there is also a crucial carotenoid isomerase gene called BnaCRTISO, which is mainly responsible for the conversion of carotenoids. Once mutated, petals may even turn milky white. 2.3 Key genes involved in pigmentation When it comes to how the flowers of B. napus display their colors, it is actually inseparable from two types of pigments-anthocyanins and carotenoids, each of which has a specific structural gene responsible for synthesis. For instance, anthocyanins mainly rely on the enzymes encoded by genes such as CHS, CHI and ANS to catalyze step by step. The synthesis of carotenoids cannot do without the participation of genes such as BnaPSY and BnaPDS3. In simple terms, it is precisely these genes that work diligently that enable the petals to eventually present the colors we see. In fact, in B. napus, flower color is not determined by structural genes themselves-what really plays a regulatory role behind the scenes are some key transcription factors. For instance, BnaA07.PAP2, BnaMYBL2 and BnaTT8 are all "regulars" in the anthocyanin synthesis pathway. Once they become active, the expression of structural genes such as CHS and ANS follows suit, and anthocyanins accumulate more and more. Interestingly, the regulation is not all positive. Inhibitory factors like BnaWRKY41-1, which usually suppress anthocyanin synthesis, can cause the petal color to darken instead once they mutate and become ineffective (Duan et al., 2018).
RkJQdWJsaXNoZXIy MjQ4ODYzNA==