Elimination of hop latent viroid upon developmental activation of pollen nucleases
Elimination of hop latent viroid upon developmental activation of pollen nucleases
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DOI：
10.1515/bc.2008.096
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发表时间：
2008-07-01
影响因子：
3.7
通讯作者：
Steger, Gerhard
中科院分区：
文献类型：
--
作者：
Matousek, Jaroslav;Orctova, Lidmila;Steger, Gerhard
啤酒花潜伏类病毒（HLVd）不通过啤酒花生殖组织和种子传播。在这里，我们描述的过程中消除HLVd啤酒花花粉的发展。HLVd在单核啤酒花花粉中繁殖，但在花粉液泡化和成熟过程中第一次花粉有丝分裂后的阶段被消除。通过RT-PCR在开花后的成熟花粉中仅检测到痕量的HLVd，并且在体外萌发的花粉中未检测到类病毒，这表明环状和线性HLVd形式完全降解。未成熟花粉中的大多数降解的HLVd RNA包括230-100个核苷酸范围内的离散产物，因此不对应于siRNA。从花粉中根除HLVd与花粉核酸酶和特异性RNA酶的发育表达相关。花粉核酸酶HBN 1的活性在液泡化过程中达到最大，在成熟花粉中下降。总RNA酶活性持续增加，直到花粉成熟的最后步骤。HBN 1 mRNA在单核小孢子期大量表达，编码300个氨基酸的蛋白质（34.1 kDa，等电点5.1）。序列比较显示HBN 1是S1样双功能植物核酸内切酶的同源物。发育激活的HBN 1和花粉核糖核酸酶可能参与了HLVd的识别和降解机制。
Hop latent viroid (HLVd) is not transmissible through hop generative tissues and seeds. Here we describe the process of HLVd elimination during development of hop pollen. HLVd propagates in uninucleate hop pollen, but is eliminated at stages following first pollen mitosis during pollen vacuolization and maturation. Only traces of HLVd were detected by RT-PCR in mature pollen after anthesis and no viroid was detectable in in vitro germinating pollen, suggesting complete degradation of circular and linear HLVd forms. The majority of the degraded HLVd RNA in immature pollen included discrete products in the range of 230-100 nucleotides and therefore did not correspond to siRNAs. HLVd eradication from pollen correlated with developmental expression of a pollen nuclease and specific RNAses. Activity of the pollen nuclease HBN1 was maximal during the vacuolization step and decreased in mature pollen. Total RNAse activity increased continuously up to the final steps of pollen maturation. HBN1 mRNA, which is abundant at the uninucleate microspore stage, encodes a protein of 300 amino acids (34.1 kDa, isoeletric point 5.1). Sequence comparisons revealed that HBN1 is a homolog of S1-like bifunctional plant endonucleases. The developmentally activated HBN1 and pollen ribonucleases could participate in the mechanism of HLVd recognition and degradation.