National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India.
Chair of Genetics and Genomics of Plants, Bielefeld University, 33615, Bielefeld, Germany.
Planta. 2022 Aug 29;256(4):67. doi: 10.1007/s00425-022-03979-z.
We identified 119 typical CaMYB encoding genes and reveal the major components of the proanthocyanidin regulatory network. CaPARs emerged as promising targets for genetic engineering toward improved agronomic traits in C. arietinum. Chickpea (Cicer arietinum) is among the eight oldest crops and has two main types, i.e., desi and kabuli, whose most obvious difference is the color of their seeds. We show that this color difference is due to differences in proanthocyanidin content of seed coats. Using a targeted approach, we performed in silico analysis, metabolite profiling, molecular, genetic, and biochemical studies to decipher the transcriptional regulatory network involved in proanthocyanidin biosynthesis in the seed coat of C. arietinum. Based on the annotated C. arietinum reference genome sequence, we identified 119 typical CaMYB encoding genes, grouped in 32 distinct clades. Two CaR2R3-MYB transcription factors, named CaPAR1 and CaPAR2, clustering with known proanthocyanidin regulators (PARs) were identified and further analyzed. The expression of CaPAR genes correlated well with the expression of the key structural proanthocyanidin biosynthesis genes CaANR and CaLAR and with proanthocyanidin levels. Protein-protein interaction studies suggest the in vivo interaction of CaPAR1 and CaPAR2 with the bHLH-type transcription factor CaTT8. Co-transfection analyses using Arabidopsis thaliana protoplasts showed that the CaPAR proteins form a MBW complex with CaTT8 and CaTTG1, able to activate the promoters of CaANR and CaLAR in planta. Finally, transgenic expression of CaPARs in the proanthocyanidin-deficient A. thaliana mutant tt2-1 leads to complementation of the transparent testa phenotype. Taken together, our results reveal main components of the proanthocyanidin regulatory network in C. arietinum and suggest that CaPARs are relevant targets of genetic engineering toward improved agronomic traits.
我们鉴定了 119 个典型的 CaMYB 编码基因，并揭示了原花青素调控网络的主要组成部分。CaPAR 作为遗传工程的有希望的靶点出现，以提高鹰嘴豆的农艺性状。鹰嘴豆（Cicer arietinum）是八大最古老的作物之一，有两种主要类型，即 Desi 和 Kabuli，它们最明显的区别是种子的颜色。我们表明，这种颜色差异是由于种皮中原花青素含量的差异。我们采用靶向方法，进行了计算机分析、代谢物分析、分子、遗传和生化研究，以破译参与鹰嘴豆种皮中原花青素生物合成的转录调控网络。基于注释的鹰嘴豆参考基因组序列，我们鉴定了 119 个典型的 CaMYB 编码基因，分为 32 个不同的分支。鉴定并进一步分析了两个 CaR2R3-MYB 转录因子，命名为 CaPAR1 和 CaPAR2，它们与已知的原花青素调控因子（PAR）聚类。CaPAR 基因的表达与关键结构原花青素生物合成基因 CaANR 和 CaLAR 的表达以及原花青素水平密切相关。蛋白-蛋白相互作用研究表明，CaPAR1 和 CaPAR2 与 bHLH 型转录因子 CaTT8 体内相互作用。使用拟南芥原生质体进行的共转染分析表明，CaPAR 蛋白与 CaTT8 和 CaTTG1 形成 MBW 复合物，能够在体内激活 CaANR 和 CaLAR 的启动子。最后，在原花青素缺乏的拟南芥突变体 tt2-1 中转基因表达 CaPAR 导致透明种皮表型的互补。总之，我们的研究结果揭示了鹰嘴豆中原花青素调控网络的主要组成部分，并表明 CaPAR 是遗传工程提高农艺性状的相关靶点。
