Identification of a new class of pistil-specific proteins of Petunia inflata that is structurally similar to, but functionally distinct from, the self-incompatibility factor HT
Identification of a new class of pistil-specific proteins of Petunia inflata that is structurally similar to, but functionally distinct from, the self-incompatibility factor HT
复制标题
DOI：
10.1007/s00438-005-0067-7
复制
发表时间：
2006-01-01
影响因子：
3.1
通讯作者：
Hirano, H
中科院分区：
文献类型：
--
作者：
Sassa, H;Hirano, H
花粉-雌蕊相互作用被认为涉及由不同蛋白质和其他分子控制的各种细胞间识别事件。最具特征的相互作用之一是在茄科、蔷薇科和玄参科中发现的基于S-RNase的配子体自交不亲和（GSI）系统。虽然这些科中雌蕊和花粉的S特异性分别由S位点编码的蛋白S-RNase和SLF/SFB决定，但单独这些蛋白不足以进行GSI反应。还需要其他因素，并将其分为三组。到目前为止，唯一已知的因素是雌蕊表达的小天冬酰胺丰富的蛋白HT-B在三个茄科属烟草，番茄和茄。HT-B是花粉排斥所需的第2组因子，但不影响S-RNase表达;其他组中的因子尚未克隆。在这里，我们确定了一类新的HT样蛋白质的风格，矮牵牛，并命名为HTL。通过选择性剪接，发现两个分离的同源HTL cDNA，HTL-A和HTL-B，来自一个基因。与HT-B一样，HTL表现出雌蕊特异性积累以及与HT的显着序列相似性，包括C-末端区域的保守半胱氨酸残基和用于细胞外定位的信号肽。然而，与HT-B不同，HTL缺乏富含天冬酰胺的结构域。因此，它代表了一类新的HT蛋白。为了确定HTL是否参与GSI功能，将HTL-A和HTL-B的RNA沉默构建体引入自交不亲和的胀囊青霉中。虽然几个转基因株系没有检测到HTL-A和HTL-B的转录水平，他们保留了正常的GSI功能，并产生大的果实后，兼容授粉。这表明，由于HTL基因单独沉默不足以影响生殖生理学，该基因在功能上不同于GSI因子HT-B。
Pollen-pistil interactions are thought to involve a wide variety of intercellular recognition events controlled by diverse proteins and other molecules. One of the best characterized interactions is the S-RNase-based gametophytic self-incompatibility (GSI) system found in Solanaceae, Rosaceae and Scrophulariaceae. Although the S specificity of the pistil and the pollen in these families is determined by the S locus-encoded proteins S-RNase and SLF/SFB, respectively, these proteins alone are not sufficient for operation of the GSI reaction. Other factors are also required and are classified into three groups. To date, the only known factor is the pistil-expressed small asparagine-rich protein HT-B in three solanaceous genera Nicotiana, Lycopersicon and Solanum. HT-B is a Group 2 factor that is required for pollen rejection but do not affect S-RNase expression; factors in the other groups have not yet cloned. Here, we identified a new class of HT-like proteins in the style of Petunia inflata and named it HTL. Through alternative splicing, it was found that two isolated homologous HTL cDNAs, HTL-A and HTL-B, derived from a single gene. Like HT-B, HTL showed pistil-specific accumulation as well as significant sequence similarity to HT including conserved cystein residues at the C-terminal region and a signal peptide for extracellular localization. However, unlike HT-B, HTL lacked an asparagine-rich domain. Thus, it represents a new class of HT proteins. To determine whether HTL is involved in GSI function, RNA silencing constructs for HTL-A and HTL-B were introduced into self-incompatible P. inflata. Although several transgenic lines showed no detectable levels of both HTL-A and HTL-B transcripts, they retained normal GSI function and produced large fruits upon compatible pollination. This suggests that since silencing of the HTL gene alone is not sufficient to affect reproductive physiology, the gene is functionally distinct from the GSI factor HT-B.