全新形态性状（Morphological novelties）的起源是进化生物学研究的热点之一。茄科酸浆属（Physalis）植物具有全新花后结构——“中国灯笼”或膨大花萼症状（ICS, inflated calyx syndrome），是花萼随着浆果的生长发育而迅速膨大的结果。该创新性状是如何起源和发育的呢？紧密围绕这一科学问题，中科院植物研究所贺超英研究组进行了一系列研究，发现“中国灯笼”的发育受到授精信号和植物激素的调控，它在茄科的进化与MADS-box基因MPF2在花器官中的异位表达和分子进化密切相关。然而，该创新结构的器官身份决定过程等尚不清楚。
近期,该研究组发现，毛酸浆euAP1 MADS-box基因MPF3和MPF2以及它们蛋白产物间的相互作用对“中国灯笼”的进化发育起重要作用。MPF3与MPF2和一些花部器官特异表达的MADS-domain蛋白互作，选择性地结合于MPF2启动子中的CArG-box，调控MPF2在花部器官中的表达。当MPF3下调后，花萼增大并叶化，但“中国灯笼”变小，花粉中的淀粉积累受阻，MPF2的表达在花萼和雄蕊中显著升高；当MPF2单基因下调后，花萼身份不变，“中国灯笼”也变小，花粉成熟严重受阻，MPF3的表达则不受影响；当MPF2和MPF3的表达双降低后，可以产生形态正常的花萼和变小的“中国灯笼”，成熟花粉的比例明显提高，但仍约有30%的花粉不能成熟。
研究结果显示，MPF3通过与MPF2的互作和对MPF2基因的遗传互作（抑制）来决定花萼身份、大小和雄性育性。此外，MPF2和MPF3可以强烈激活PFINV4基因，它的直系同源基因在水稻等植物中编码糖分解转运途径中的关键酶。在进化过程中MPF3受到正选择，序列的歧化改变了其结合DNA和蛋白质的特异性，进而获得全新的目标基因和互作蛋白，从而使其获得了在“中国灯笼”发育和雄性育性决定中的新功能。以上研究结果进一步完善了对酸浆属“中国灯笼”进化发育分子机制和调控网络的认识，并为被子植物中euAP1基因的功能进化提供了新证据。
该研究结果于6月21日在线发表在The Plant Cell（Zhao et al. , doi: 10.1105/tpc.113.111757）期刊上。研究组博士研究生赵婧和博士后田颖为该研究论文的并列第一作者。
该研究得到了中科院“百人计划”、国家自然科学基金委等项目的资助。（生物谷 ）
毛酸浆“中国灯笼”表型及其发育的调控网络（左）毛酸浆“中国灯笼”表型。（右）MPF3-相关的互作调控网络。
生物谷推荐的英文摘要
The Plant Cell
Jing Zhao, Ying Tiana, Ji-Si Zhang, Man Zhao, Pichang Gong, Simone Riss, Rainer Saedler and Chaoying He
The euAP1 Protein MPF3 Represses MPF2 to Specify Floral Calyx Identity and Displays Crucial Roles in Chinese Lantern Development in Physalis
The Chinese lantern phenotype or inflated calyx syndrome (ICS) is a postfloral morphological novelty in Physalis. Its origin is associated with the heterotopic expression of the MADS box gene 2 from Physalis floridana (MPF2) in floral organs, yet the process underlying its identity remains elusive. Here, we show that MPF3, which is expressed specifically in floral tissues, encodes a core eudicot APETALA1-like (euAP1) MADS-domain protein. MPF3 was primarily localized to the nucleus, and it interacted with MPF2 and some floral MADS-domain proteins to selectively bind the CC-A-rich-GG (CArG) boxes in the MPF2 promoter. Downregulating MPF3 resulted in a dramatic elevation in MPF2 in the calyces and androecium, leading to enlarged and leaf-like floral calyces; however, the postfloral lantern was smaller and deformed. Starch accumulation in pollen was blocked. MPF3 MPF2 double knockdowns showed normal floral calyces and more mature pollen than those found in plants in which either MPF3 or MPF2 was downregulated. Therefore, MPF3 specifies calyx identity and regulates ICS formation and male fertility through interactions with MPF2/MPF2. Furthermore, both genes were found to activate Physalis floridana invertase gene 4 homolog, which encodes an invertase cleaving Suc, a putative key gene in sugar partitioning. The novel role of the MPF3-MPF2 regulatory circuit in male fertility is integral to the origin of ICS. Our results shed light on the evolution and development of ICS in Physalis and on the functional evolution of euAP1s in angiosperms.
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