Hu Jin-Yong, Saedler Heinz
Department of Molecular Plant Genetics, Max-Planck-Institute for Plant Breeding Research, Cologne, Germany.
Mol Biol Evol. 2007 Nov;24(11):2443-53. doi: 10.1093/molbev/msm177. Epub 2007 Sep 6.
Species that express the inflated calyx syndrome (ICS) are found in several genera of the Solanaceae. The MADS-box protein MPF2, together with the plant hormones cytokinin and gibberellin, has been shown to be responsible for this trait in Physalis floridana. We have used sequence data from 114 species belonging to 35 genera to construct a molecular phylogeny of Solanaceae. Apart from the 2 Witheringia species analyzed, species within a given genus cluster together on the resulting cladogram. Witheringia solanacea is embedded within the Physalinae, but Witheringia coccoloboides is placed basal to the Iochrominae. The ICS trait seems to be of multiple origins both within the Solanaceae and the Physaleae. Surprisingly, expression of MPF2-like genes in floral organs appears to be plesiomorphic in both the Physaleae and the Capsiceae. Some species in these tribes that show neither ICS nor calyx accrescence fail to express the MPF2-like gene in floral organs. Among those that do express this gene in the calyx are the species Capsicum baccatum, Lycianthes biflora, Tubocapsicum anomalum, W. solanacea, and Vassobia breviflora, all of which form small calyces that do not respond to externally applied hormones. The plesiomorphic nature of MPF2-like gene expression in the calyx of the Physaleae and Capsiceae raises the possibility that originally ICS also was actually a plesiomorphic character in these 2 groups. However, this trait might have undergone changes in a number of species due to secondary loss of components in ICS formation, like hormone response of calyx development. These findings are discussed in an evolutionary context of a molecular pathway leading to ICS.
在茄科的几个属中发现了表现出膨大花萼综合征（ICS）的物种。MADS盒蛋白MPF2与植物激素细胞分裂素和赤霉素一起，已被证明是佛罗里达酸浆（Physalis floridana）中这一性状的成因。我们利用了来自35个属的114个物种的序列数据构建了茄科的分子系统发育树。除了分析的2个威氏茄属（Witheringia）物种外，给定属内的物种在生成的分支图上聚集在一起。茄叶威氏茄（Witheringia solanacea）嵌入酸浆亚族（Physalinae）中，但科科洛博伊德威氏茄（Witheringia coccoloboides）位于异色茄亚族（Iochrominae）的基部。ICS性状在茄科和酸浆族（Physaleae）中似乎有多个起源。令人惊讶的是，MPF2样基因在花器官中的表达在酸浆族和辣椒族（Capsiceae）中似乎都是原始的。这些族中一些既不表现出ICS也不表现出花萼增大的物种在花器官中不表达MPF2样基因。在花萼中表达该基因的物种有辣椒（Capsicum baccatum）、双花红丝线（Lycianthes biflora）、异形茄（Tubocapsicum anomalum）、茄叶威氏茄、短花瓦索比亚茄（Vassobia breviflora），所有这些物种都形成小的花萼，对外源施加的激素无反应。MPF2样基因在酸浆族和辣椒族花萼中的原始性质增加了这样一种可能性，即最初ICS在这两个类群中实际上也是一个原始特征。然而，由于ICS形成过程中成分的二次丧失，如萼片发育的激素反应，这一性状可能在许多物种中发生了变化。这些发现是在导致ICS的分子途径的进化背景下进行讨论的。
