Developmental evolution of flowering plant pollen tube cell walls: callose synthase (CalS) gene expression patterns
Developmental evolution of flowering plant pollen tube cell walls: callose synthase (CalS) gene expression patterns
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DOI：
10.1186/2041-9139-2-14
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发表时间：
2011-01-01
期刊：
影响因子：
4.1
通讯作者：
Williams, Joseph H.
中科院分区：
文献类型：
--
作者：
Abercrombie, Jason M.;O'Meara, Brian C.;Williams, Joseph H.
背景：被子植物快速生殖周期的起源有许多创新。早期的一个关键步骤涉及修改祖先的短且生长缓慢的花粉管，以便将精子更快、更长距离地运输到卵子。与这种转变相关的是被子植物花粉管的主要胼胝质（1，3-β-葡聚糖）壁和隔膜（胼胝质塞）。胼胝质合成由胼胝质合成酶（CalS）介导。在拟南芥的12个CalS基因家族中，只有一个（CalS 5）与花粉管胼胝质直接连锁。CalS 5的直系同源物存在于几个单子叶植物和真双子叶植物基因组，但很少有人知道CalS 5的进化起源或它的祖先的功能可能已经been.Results：我们调查了CalS在花粉和花粉管中的表达所选择的非开花种子植物（裸子植物）和被子植物的谱系内的单子叶植物/真双子叶植物的节点下分歧。首先，我们确定了来自水盾草（Cabomba caroliniana）（睡莲目（Nymphaeales））的CalS 5直向同源物（CcCalS 5）的近全长编码序列。半定量RT-PCR结果表明，CcCalS 5在几种营养组织中表达较低，但在成熟花粉中表达较强。CalS成绩单中检测到的几个物种内的Nymphaeales和Austrobaileyales的花粉管，和比较分析与一组不同的基因组序列的同源性CalS 5。我们还报告了来自Amborella的推定CalS 5直系同源物的计算机证据。在裸子植物中，CalS 5的成绩单回收发芽花粉的买麻藤和银杏，但一个新的CalS paradigm，而不是从发芽花粉扩增的Pinustaeda.Conclusion：发现CalS 5是主导的胼胝质合成酶的早期发散和模式系统的被子植物的花粉管是一个指标的同源性，他们的新的胼胝质花粉管壁和胼胝质塞。这些数据表明，CalS 5在早期种子植物中具有瞬时表达和花粉特异性功能，然后在现存被子植物的祖先中被招募到花粉管壁内的新表达模式和功能。
Background: A number of innovations underlie the origin of rapid reproductive cycles in angiosperms. A critical early step involved the modification of an ancestrally short and slow-growing pollen tube for faster and longer distance transport of sperm to egg. Associated with this shift are the predominantly callose (1,3-beta-glucan) walls and septae (callose plugs) of angiosperm pollen tubes. Callose synthesis is mediated by callose synthase (CalS). Of 12 CalS gene family members in Arabidopsis, only one (CalS5) has been directly linked to pollen tube callose. CalS5 orthologues are present in several monocot and eudicot genomes, but little is known about the evolutionary origin of CalS5 or what its ancestral function may have been.Results: We investigated expression of CalS in pollen and pollen tubes of selected non-flowering seed plants (gymnosperms) and angiosperms within lineages that diverged below the monocot/eudicot node. First, we determined the nearly full length coding sequence of a CalS5 orthologue from Cabomba caroliniana (CcCalS5) (Nymphaeales). Semi-quantitative RT-PCR demonstrated low CcCalS5 expression within several vegetative tissues, but strong expression in mature pollen. CalS transcripts were detected in pollen tubes of several species within Nymphaeales and Austrobaileyales, and comparative analyses with a phylogenetically diverse group of sequenced genomes indicated homology to CalS5. We also report in silico evidence of a putative CalS5 orthologue from Amborella. Among gymnosperms, CalS5 transcripts were recovered from germinating pollen of Gnetum and Ginkgo, but a novel CalS paralog was instead amplified from germinating pollen of Pinus taeda.Conclusion: The finding that CalS5 is the predominant callose synthase in pollen tubes of both early-diverging and model system angiosperms is an indicator of the homology of their novel callosic pollen tube walls and callose plugs. The data suggest that CalS5 had transient expression and pollen-specific functions in early seed plants and was then recruited to novel expression patterns and functions within pollen tube walls in an ancestor of extant angiosperms.