Institute of Fruit Tree Research, Guangdong Academy of Agricultural Sciences, Key Laboratory of South Subtropical Fruit Biology and Genetic Resource Utilization, Ministry of Agriculture and Rural Affairs, Guangdong Provincial Key Laboratory of Tropical and Subtropical Fruit Tree Research, Guangzhou, Guangdong, China.
School of Life Sciences, Guangzhou University, Guangzhou, Guangdong, China.
PeerJ. 2022 Nov 1;10:e14165. doi: 10.7717/peerj.14165. eCollection 2022.
Self-incompatibility (SI) is a major issue in dragon fruit () breeding and production. Therefore, a better understanding of the dragon fruit SI mechanism is needed to improve breeding efficiency and ultimate production costs. To reveal the underlying mechanisms of SI in dragon fruit, plant anatomy, RNA sequencing-based transcriptomic analysis, and multiple bioinformatic approaches were used to analyze gene expression in the pistils of the self-pollinated and cross-pollinated dragon fruit flowers at different intervals of time after pollination. Using fluorescence microscopy, we observed that the pollen of 'Hongshuijing', a self-incompatible dragon fruit variety (), germinated on its own stigma. However, the pollen tube elongation has ceased at 1/2 of the style, confirming that dragon fruit experiences gametophyte self-incompatibility (GSI). We found that the pollen tube elongation was inhibited by self-style glycoproteins in the SI variety, indicating that glycoproteins were involved in SI. That is to say the female S factor should be homologous of S-RNase or PrsS ( stigma S factor), both of which are glycoproteins and are the female S factors of the two known GSI mechanism respectively. Bioinformatics analyses indicated that among the 43,954 assembled unigenes from pistil, there were six S-RNase genes, while 158 F-box genes were identified from a pollen transcriptomic dataset. There were no P. type S genes discovered. Thus, the identified S-RNase and F-box represent the candidate female and male S genes, respectively. Analysis of differentially expressed genes (DEGs) between the self and cross-pollinated pistils at different time intervals led to the identification of 6,353 genes. We then used a weighted gene co-expression network analysis (WGCNA) to find some non-S locus genes in SI responses in dragon fruit. Additionally, 13 transcription factors (TFs) (, two , two and two ) were identified to be involved in dragon fruit GSI. Thus, we uncovered candidate S and non-S genes and predicted more SI-related genes for a more detailed investigation of the molecular mechanism of dragon fruit SI. Our findings suggest that dragon fruit possesses a GSI system and involves some unique regulators. This study lays the groundwork for future research into SI mechanisms in dragon fruit and other plant species.
自交不亲和性 (SI) 是火龙果繁殖和生产中的一个主要问题。因此，需要更好地了解火龙果 SI 机制，以提高繁殖效率和最终生产成本。为了揭示火龙果 SI 的潜在机制，我们使用植物解剖学、基于 RNA 测序的转录组分析以及多种生物信息学方法，分析了授粉后不同时间自交和杂交火龙果花朵雌蕊中的基因表达。通过荧光显微镜观察，我们发现自交不亲和火龙果品种“红水晶”的花粉在其自身柱头上萌发。然而，花粉管伸长在花柱的 1/2 处停止，证实火龙果经历配子体自交不亲和 (GSI)。我们发现，自交品种中花柱糖蛋白抑制花粉管伸长，表明糖蛋白参与 SI。也就是说，雌性 S 因子应该与 S-RNase 或 PrsS（柱头 S 因子）同源，它们都是糖蛋白，分别是两种已知 GSI 机制的雌性 S 因子。生物信息学分析表明，在来自雌蕊的 43954 个组装的 unigenes 中，有 6 个 S-RNase 基因，而从花粉转录组数据集鉴定出 158 个 F-box 基因。没有发现 P 型 S 基因。因此，鉴定出的 S-RNase 和 F-box 分别代表候选雌性和雄性 S 基因。对自交和杂交雌蕊在不同时间间隔的差异表达基因 (DEGs) 进行分析，鉴定出 6353 个基因。然后，我们使用加权基因共表达网络分析 (WGCNA) 在火龙果 SI 反应中找到一些非 S 位点基因。此外，鉴定出 13 个转录因子 (TF)（两个 、两个 、两个 和两个 ）参与火龙果 GSI。因此，我们发现了候选 S 和非 S 基因，并预测了更多与 SI 相关的基因，以更详细地研究火龙果 SI 的分子机制。我们的研究结果表明，火龙果具有 GSI 系统，并涉及一些独特的调节剂。这项研究为未来研究火龙果和其他植物物种的 SI 机制奠定了基础。
