Vegetable Crops Research Unit, USDA-ARS, Department of Horticulture, University of Wisconsin at Madison, 1575 Linden Dr., Madison, WI, 53706, USA.
Department of Crop Sciences, University of Illinois at Urbana-Champaign, 1201 W. Gregory Dr., Urbana, IL, 61801, USA.
Theor Appl Genet. 2023 Mar 13;136(3):55. doi: 10.1007/s00122-023-04275-4.
Anthocyanin3 inhibits the anthocyanin and monolignol pathways in maize. Transposon-tagging, RNA-sequencing, and GST-pulldown assays determine Anthocyanin3 may be R3-MYB repressor gene Mybr97. Anthocyanins are colorful molecules receiving recent attention due to their numerous health benefits and applications as natural colorants and nutraceuticals. Purple corn is being investigated as a more economical source of anthocyanins. Anthocyanin3 (A3) is a known recessive intensifier of anthocyanin pigmentation in maize. In this study, anthocyanin content was elevated 100-fold in recessive a3 plants. Two approaches were used to discover candidates involved with the a3 intense purple plant phenotype. First, a large-scale transposon-tagging population was created with a Dissociation (Ds) insertion in the nearby Anthocyanin1 gene. A de novo a3-m1::Ds mutant was generated, and the transposon insertion was found to be located in the promoter of Mybr97, which has homology to R3-MYB repressor CAPRICE in Arabidopsis. Second, a bulked segregant RNA-sequencing population found expression differences between pools of green A3 plants and purple a3 plants. All characterized anthocyanin biosynthetic genes were upregulated in a3 plants along with several genes of the monolignol pathway. Mybr97 was highly downregulated in a3 plants, suggesting its role as a negative regulator of the anthocyanin pathway. Photosynthesis-related gene expression was reduced in a3 plants through an unknown mechanism. Numerous transcription factors and biosynthetic genes were also upregulated and need further investigation. Mybr97 may inhibit anthocyanin synthesis by associating with basic helix-loop helix transcription factors like Booster1. Overall, Mybr97 is the most likely candidate gene for the A3 locus. A3 has a profound effect on the maize plant and has many favorable implications for crop protection, human health, and natural colorant production.
花色素苷 3 抑制玉米中的花色素苷和单酚途径。转座子标记、RNA 测序和 GST 下拉测定表明，花色素苷 3 可能是 R3-MYB 阻遏基因 Mybr97。由于花色素苷具有多种健康益处，并且可用作天然着色剂和营养保健品，因此最近受到了广泛关注。正在研究紫玉米作为花色素苷更经济的来源。花色素苷 3（A3）是玉米中已知的隐性增强花色苷色素沉着的物质。在这项研究中，隐性 a3 植株中的花色苷含量提高了 100 倍。使用两种方法来发现与 a3 强烈紫色植物表型相关的候选物。首先，在附近的 Anthocyanin1 基因中使用 Dissociation（Ds）插入物创建了一个大型转座子标记种群。生成了一个新的 a3-m1::Ds 突变体，发现转座子插入位于 Mybr97 的启动子中，Mybr97 与拟南芥中的 R3-MYB 阻遏物 CAPRICE 具有同源性。其次，大量分离 RNA 测序群体发现绿色 A3 植物和紫色 a3 植物之间的表达差异。所有特征性的花色素苷生物合成基因在 a3 植物中上调，同时单酚途径的几个基因也上调。Mybr97 在 a3 植物中高度下调，表明其作为花色素苷途径的负调节剂的作用。通过未知机制，a3 植物中光合作用相关基因的表达减少。还上调了许多转录因子和生物合成基因，需要进一步研究。Mybr97 可能通过与 Booster1 等碱性螺旋-环-螺旋转录因子结合来抑制花色素苷的合成。总体而言，Mybr97 是 A3 基因座最可能的候选基因。A3 对玉米植株有深远的影响，对作物保护、人类健康和天然着色剂生产具有许多有利的影响。
