MAIN CONCLUSION Genome-wide identification, tissue-specific expression analysis and functional characterization of selected genes containing the pear Pollen Olea europaea I domain reveal their roles in pollen tube growth. Genes containing the Pollen Olea europaea I (POE) domain play crucial roles in diverse growth and developmental processes. Nevertheless, the specific functions of POE family members in progression of pollen tube growth (PTG) remain uncharacterized. We identified 45 PbrPOE genes in the pear (Pyrus bretschneideri) genome, clustered into seven subclasses. PbrPOE genes contained 1 to 11 exons and 0 to 10 introns, with exon/intron structure mostly conserved within each subclass. Whole-genome duplication has mainly contributed to the duplication pattern of PbrPOE genes in pear. Expression profiles of 45 PbrPOE genes in 12 different pear tissues revealed that six PbrPOE genes (PbrPOE6, 12, 21, 29, 35 and 41) of subclass B were highly expressed during the growth of the pear pollen tube in vitro. PbrPOE21 was selected for further functional analysis on the basis of its high and differential expression pattern in pollen. Antisense oligodeoxynucleotide assays demonstrated that PTG was augmented in vitro when PbrPOE21 expression was significantly inhibited. Moreover, pollen tube length in vitro was reduced when PbrPOE21 was transitorily over-expressed using particle bombardment technology. Exogenous PbrPOE21 recombinant protein inhibited PTG in vitro at an optimum concentration of 1.8 µM. PbrPOE21 also affected reactive oxygen species content in the pear pollen tube apex. We suggest that PbrPOE21 inhibits PTG in vitro by altering apical reactive oxygen species content.

中文翻译：

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PbrPOE21通过改变顶端活性氧含量抑制体外梨花粉管生长

主要结论 包含梨花粉油橄榄 I 结构域的选定基因的全基因组鉴定、组织特异性表达分析和功能表征揭示了它们在花粉管生长中的作用。含有花粉油橄榄 I (POE) 域的基因在不同的生长和发育过程中起着至关重要的作用。然而，POE 家族成员在花粉管生长 (PTG) 进展中的特定功能仍未得到表征。我们在梨 (Pyrus bretschneideri) 基因组中鉴定了 45 个 PbrPOE 基因，分为七个亚类。PbrPOE 基因包含 1 到 11 个外显子和 0 到 10 个内含子，每个亚类中的外显子/内含子结构大多是保守的。全基因组重复主要促成了梨中 PbrPOE 基因的重复模式。45个PbrPOE基因在12个不同梨组织中的表达谱显示，在梨花粉管体外生长过程中，B亚类的6个PbrPOE基因（PbrPOE6、12、21、29、35和41）高表达。基于其在花粉中的高和差异表达模式选择PbrPOE21进行进一步的功能分析。反义寡脱氧核苷酸测定表明，当 PbrPOE21 表达受到显着抑制时，PTG 在体外得到增强。此外，当使用粒子轰击技术暂时过表达 PbrPOE21 时，体外花粉管长度减少。外源 PbrPOE21 重组蛋白在体外以 1.8 µM 的最佳浓度抑制 PTG。PbrPOE21 还影响梨花粉管顶端的活性氧含量。