Heterotopic expression of class B floral homeotic genes supports a modified ABC model for tulip (Tulipa gesneriana)
Heterotopic expression of class B floral homeotic genes supports a modified ABC model for tulip (Tulipa gesneriana)
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DOI：
10.1023/a:1025070827979
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发表时间：
2003-07-01
影响因子：
5.1
通讯作者：
Theissen, G
中科院分区：
文献类型：
--
作者：
Kanno, A;Saeki, H;Theissen, G
在高等有子叶被子植物中，花器官通常排列在四个不同的轮生中，包括萼片、花瓣、雄蕊和心皮。根据ABC模型，这些器官的特性分别由A、A+B、B+C和C类花的同源异型基因决定。许多百合科植物的花被片有两个外轮生的几乎相同的花瓣状器官，称为花被片，与真雄蕊的花冠和花瓣轮生不同。为了解释百合科的花形态，van Tunen等人。(1993)提出了一个修正的ABC模型，并以郁金香为例。根据这个模型，B类基因不仅在轮生2和3中表达，而且在轮生1中也表达。因此，轮生1和2的器官都表达A类和B类基因，从而获得相同的花瓣身份。为了验证这个改进的ABC模型，我们从郁金香中克隆并鉴定了可能的B类基因。鉴定出2个DEF-样基因和1个GLO样基因，分别命名为TGDEFA、TGDEFB和TGGLO。Northern杂交分析表明，所有这些基因都在轮生1、2和3(内外被片和雄蕊)中表达，从而证实了改进的ABC模型。此外，这些实验还表明，TGGLO在心皮、叶、茎和苞片中也有微弱的表达。凝胶滞留分析表明，TGGLO单独以同源二聚体的形式与DNA结合。相反，TGDEFA和TGDEFB不能均二聚，而是与PI形成杂二聚体。百合中也有类似GLO蛋白的同源二聚现象的报道，这表明这种现象在百合科植物中甚至在单子叶植物中都是保守的。
In higher eudicotyledonous angiosperms the floral organs are typically arranged in four different whorls, containing sepals, petals, stamens and carpels. According to the ABC model, the identity of these organs is specified by floral homeotic genes of class A, A+B, B+C and C, respectively. In contrast to the sepal and petal whorls of eudicots, the perianths of many plants from the Liliaceae family have two outer whorls of almost identical petaloid organs, called tepals. To explain the Liliaceae flower morphology, van Tunen et al. (1993) proposed a modified ABC model, exemplified with tulip. According to this model, class B genes are not only expressed in whorls 2 and 3, but also in whorl 1. Thus the organs of both whorls 1 and 2 express class A plus class B genes and, therefore, get the same petaloid identity. To test this modified ABC model we have cloned and characterized putative class B genes from tulip. Two DEF- and one GLO-like gene were identified, named TGDEFA, TGDEFB and TGGLO. Northern hybridization analysis showed that all of these genes are expressed in whorls 1, 2 and 3 (outer and inner tepals and stamens), thus corroborating the modified ABC model. In addition, these experiments demonstrated that TGGLO is also weakly expressed in carpels, leaves, stems and bracts. Gel retardation assays revealed that TGGLO alone binds to DNA as a homodimer. In contrast, TGDEFA and TGDEFB cannot homodimerize, but make heterodimers with PI. Homodimerization of GLO- like protein has also been reported for lily, suggesting that this phenomenon is conserved within Liliaceae plants or even monocot species.