B-class MADS-box genes in trioecious papaya:: two paleoAP3 paralogs, CpTM6-1 and CpTM6-2, and a PI ortholog CpPI
B-class MADS-box genes in trioecious papaya:: two paleoAP3 paralogs, CpTM6-1 and CpTM6-2, and a PI ortholog CpPI
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DOI：
10.1007/s00425-007-0653-5
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发表时间：
2008-03-01
期刊：
影响因子：
4.3
通讯作者：
Ming, Ray
中科院分区：
文献类型：
--
作者：
Ackerman, Christine M.;Yu, Qingyi;Ming, Ray
在花发育的ABC模型中，B功能器官识别基因作用于花的第二和第三轮，控制花瓣和雄蕊的识别。番木瓜雌雄异株具有雄花、雌花和两性花，是检测雌雄异株植物中B类基因表达模式的理想系统。利用MADS box基因特异简并引物克隆了番木瓜B类基因CpTM 6 -1、CpTM 6 -2和CpPI，并对阳性克隆进行了cDNA文库筛选和序列测定。虽然系统发育分析表明，CpPI是拟南芥基因PI的直系同源物，CpTM 6 -1和CpTM 6 -2基因座是旁系同源TM 6谱系的代表，其包含不同于在拟南芥中观察到的euAP 3基因的paleoAP 3基序。这两个旁系同源物似乎起源于大约1340万年前（mya）发生的串联重复（bootstrap range 13.36 +/- 2.42）。原位杂交和RT-PCR结果表明，番木瓜B类基因在所有花器官原基的幼花中均得到高表达。随着花器官的发育，所有三个B类基因在所有三种性别类型的花瓣和两性花和雄花的雄蕊中均高度表达。CpTM 6 -1在萼片和心皮中表达量较低，CpTM 6 -2在萼片中表达量较低，在叶片中表达量较高。我们的研究结果表明，B类基因同源物在三叶虫花中可以按照ABC模型预测的那样发挥功能，但CpTM 6 -1、CpTM 6 -2和CpPI的差异表达表明它们在重复事件后功能的多样化。
In the ABC model of flower development, B function organ-identity genes act in the second and third whorls of the flower to control petal and stamen identity. The trioecious papaya has male, female, and hermaphrodite flowers and is an ideal system for testing the B-class gene expression patterns in trioecious plants. We cloned papaya B-class genes, CpTM6-1, CpTM6-2, and CpPI, using MADS box gene specific degenerate primers followed by cDNA library screening and sequencing of positive clones. While phylogenetic analyses show that CpPI is the ortholog of the Arabidopsis gene PI, the CpTM6-1 and CpTM6-2 loci are representatives of the paralogous TM6 lineage that contain paleoAP3 motifs unlike the euAP3 gene observed in Arabidopsis. These two paralogs appeared to have originated from a tandem duplication occurred approximately 13.4 million year ago (mya) (bootstrap range 13.36 +/- 2.42). In-situ hybridization and RT-PCR showed that the papaya B-class genes were highly expressed in young flowers across all floral organ primordia. As the flower organs developed, all three B-class genes were highly expressed in petals of all three-sex types and in stamens of hermaphrodite and male flowers. CpTM6-1 expressed at low levels in sepals and carpels, whereas CpTM6-2 expressed at a low level in sepals and at a high level in leaves. Our results showed that B-class gene homologs could function as predicted by the ABC model in trioecous flowers but differential expressions of CpTM6-1, and CpTM6-2, and CpPI suggested the diversification of their functions after the duplication events.