Zhang Dajian, Zhao Meixia, Li Shuai, Sun Lianjun, Wang Weidong, Cai Chunmei, Dierking Emily C, Ma Jianxin
Department of Agronomy, Purdue University, West Lafayette, IN, 47906, USA.
College of Life Sciences, Qingdao Agricultural University, Qingdao, Shandong, 266109, China.
Plant J. 2017 Jun;90(6):1120-1133. doi: 10.1111/tpj.13533. Epub 2017 Apr 12.
Many plants have undergone whole genome duplication (WGD). However, how regulatory networks underlying a particular trait are reshaped in polyploids has not been experimentally investigated. Here we show that the regulatory pathways modulating seed oil content, which involve WRINKLED1 (WRI1), LEAFY COTYLEDON1 (LEC1), and LEC2 in Arabidopsis, have been modified in the palaeopolyploid soybean. Such modifications include functional reduction of GmWRI1b of the GmWRI1a/GmWRI1b homoeologous pair relevant to WRI1, complementary non-allelic dosage effects of the GmLEC1a/GmLEC1b homoeologous pair relevant to LEC1, pseudogenization of the singleton GmLEC2 relevant to LEC2, and the rise of the LEC2-like function of GmABI3b, contrasting to its homoeolog GmABI3a, which maintains the ABSCISIC ACID INSENSITIVE 3 (ABI3)-like function in modulating seed maturation and dormancy. The function of GmABI3b in modulating seed oil biosynthesis was fulfilled by direct binding to a RY (CATGCA) cis-regulatory element in the GmWRI1a promoter, which was absent in the GmWRI1b promoter, resulting in reduction of the GmWRI1b expression. Nevertheless, the three regulators each exhibited similar intensities of purifying selection to their respective duplicates since these pairs were formed by a WGD event that is proposed to have occurred approximately 13 million years ago (mya), suggesting that the differentiation in spatiotemporal expression between the duplicated genes is more likely to be the outcome of neutral variation in regulatory sequences. This study thus exemplifies the plasticity, dynamics, and novelty of regulatory networks mediated by WGD.
许多植物都经历了全基因组复制（WGD）。然而，多倍体中特定性状的调控网络是如何重塑的，尚未进行实验研究。在这里，我们表明，在古多倍体大豆中，调控种子油含量的途径已经发生了改变，这些途径在拟南芥中涉及皱叶1（WRI1）、叶状子叶1（LEC1）和LEC2。这种改变包括与WRI1相关的GmWRI1a/GmWRI1b同源对中的GmWRI1b功能降低，与LEC1相关的GmLEC1a/GmLEC1b同源对的互补非等位剂量效应，与LEC2相关的单拷贝GmLEC2的假基因化，以及GmABI3b的LEC2样功能的增强，这与其同源基因GmABI3a形成对比，GmABI3a在调节种子成熟和休眠方面保持脱落酸不敏感3（ABI3）样功能。GmABI3b在调节种子油生物合成中的功能是通过直接结合GmWRI1a启动子中的RY（CATGCA）顺式调控元件来实现的，而GmWRI1b启动子中不存在该元件，导致GmWRI1b表达降低。然而，这三个调控因子各自对其各自的重复基因表现出相似强度的纯化选择，因为这些对是由大约1300万年前（mya）发生的一次WGD事件形成的，这表明重复基因之间时空表达的差异更可能是调控序列中性变异的结果。因此，这项研究例证了由WGD介导的调控网络的可塑性、动态性和新颖性。
