Innovation of a Regulatory Mechanism Modulating Semi-determinate Stem Growth through Artificial Selection in Soybean.
Innovation of a Regulatory Mechanism Modulating Semi-determinate Stem Growth through Artificial Selection in Soybean.
复制标题
DOI：
10.1371/journal.pgen.1005818
复制
发表时间：
2016-01
期刊：
影响因子：
4.5
通讯作者：
Ma J
中科院分区：
文献类型：
--
作者：
Liu Y;Zhang D;Ping J;Li S;Chen Z;Ma J
已经证明，拟南芥中的终末开花 1 (TFL1) 及其在其他植物中的功能直系同源物通过其抑制茎尖分生组织 (SAM) 中的花识别基因的特异性表达来指定不确定的茎生长，并且这些功能对应物的功能丧失突变导致 SAM 从营养状态转变为生殖状态，这对于终末开花的起始和形成确定茎至关重要。然而，关于半决定茎（其产生与在有限植物中观察到的相似的末端总状花序）如何在任何开花植物中具体化，人们知之甚少。在这里，我们表明大豆的半决定性是通过 SAM 中 TFL1 的功能直系同源 Dt1 的转录抑制来调节的。这种抑制是通过最近启用的 Dt2 的时空表达来实现的，Dt2 是 APETALA1/FRUITFULL 直向同源物的祖先形式，它编码直接与 Dt1 调节序列结合的 MADS-box 因子。此外，Dt2 触发 SAM 中假定的 SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (GmSOC1) 的共表达，其中 GmSOC1 与 Dt2 相互作用，并且还直接与 Dt1 调控序列结合。 Dt2 和 Dt1 在确定性 (tfl1) 拟南芥突变体中的异源表达能够产生半确定性，但 tfl1 和 soc1 背景中两个基因的相同形式会产生不确定的茎，表明 Dt2 和 SOC1 都是 Dt1 转录抑制所必需的。然而，在拟南芥中Dt2的表达无法抑制TFL1，这进一步证明了大豆茎生长调控机制的进化新颖性。与“绿色革命”半矮化谷物类似，半决定性大豆品种具有抗倒伏性，特别适合在高肥力和灌溉环境中种植。然而，在任何开花植物中，半决定性茎生长的分子机制尚未被破译。我们证明，半决定性起源于大豆中古老 MADS-box 基因时空表达的创新以及其相互作用基因时空表达的随之变化，这种变化发生在大豆驯化后并通过育种选择。这项研究的结果不仅为通过人工选择重塑茎生长习性的分子机制的进化新颖性提供了新的见解，而且还展示了这种创新机制在其他作物茎结构分子设计中的潜在应用，以增强适应性和产量潜力。
It has been demonstrated that Terminal Flowering 1 (TFL1) in Arabidopsis and its functional orthologs in other plants specify indeterminate stem growth through their specific expression that represses floral identity genes in shoot apical meristems (SAMs), and that the loss-of-function mutations at these functional counterparts result in the transition of SAMs from the vegetative to reproductive state that is essential for initiation of terminal flowering and thus formation of determinate stems. However, little is known regarding how semi-determinate stems, which produce terminal racemes similar to those observed in determinate plants, are specified in any flowering plants. Here we show that semi-determinacy in soybean is modulated by transcriptional repression of Dt1, the functional ortholog of TFL1, in SAMs. Such repression is fulfilled by recently enabled spatiotemporal expression of Dt2, an ancestral form of the APETALA1/FRUITFULL orthologs, which encodes a MADS-box factor directly binding to the regulatory sequence of Dt1. In addition, Dt2 triggers co-expression of the putative SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (GmSOC1) in SAMs, where GmSOC1 interacts with Dt2, and also directly binds to the Dt1 regulatory sequence. Heterologous expression of Dt2 and Dt1 in determinate (tfl1) Arabidopsis mutants enables creation of semi-determinacy, but the same forms of the two genes in the tfl1 and soc1 background produce indeterminate stems, suggesting that Dt2 and SOC1 both are essential for transcriptional repression of Dt1. Nevertheless, the expression of Dt2 is unable to repress TFL1 in Arabidopsis, further demonstrating the evolutionary novelty of the regulatory mechanism underlying stem growth in soybean. Similar to the “green revolution” semi-dwarf cereals, semi-determinate soybean varieties are lodging-resistant and particularly suitable for planting in high fertility and irrigated environments. Nevertheless, molecular mechanisms underlying semi-determinate stem growth have not been deciphered in any flowering plants. We demonstrate that semi-determinacy is originated from an innovation of spatiotemporal expression of an ancient MADS-box gene and consequent changes of spatiotemporal expression of its interacting genes in soybean, which occurred post-domestication of soybean and selected by breeding. The findings from this study not only provides new insights into the evolutionary novelty of molecular mechanisms regulating stem growth habit reshaped by artificial selection, but also exhibited potential application of such an innovative mechanism for molecular design of stem architecture in other crops towards enhanced adaptability and yield potential.