DataSheet7_Maternal body condition and season influence RNA deposition in the oocytes of alfalfa leafcutting bees (Megachile rotundata).xlsx

Maternal effects are an important source of phenotypic variance, whereby females influence offspring developmental trajectory beyond direct genetic contributions, often in response to changing environmental conditions. However, relatively little is known about the mechanisms by which maternal experience is translated into molecular signals that shape offspring development. One such signal may be maternal RNA transcripts (mRNAs and miRNAs) deposited into maturing oocytes. These regulate the earliest stages of development of all animals, but are understudied in most insects. Here we investigated the effects of female internal (body condition) and external (time of season) environmental conditions on maternal RNA in the maturing oocytes and 24-h-old eggs (24-h eggs) of alfalfa leafcutting bees. Using gene expression and WGCNA analysis, we found that females adjust the quantity of mRNAs related to protein phosphorylation, transcriptional regulation, and nuclease activity deposited into maturing oocytes in response to both poor body condition and shorter day lengths that accompany the late season. However, the magnitude of these changes was higher for time of season. Females also adjusted miRNA deposition in response to seasonal changes, but not body condition. We did not observe significant changes in maternal RNAs in response to either body condition or time of season in 24-h eggs, which were past the maternal-to-zygotic transition. Our results suggest that females adjust the RNA transcripts they provide for offspring to regulate development in response to both internal and external environmental cues. Variation in maternal RNAs may, therefore, be important for regulating offspring phenotype in response to environmental change.

母体效应（maternal effects）是表型变异的重要来源，即雌性个体除通过直接遗传贡献影响子代发育轨迹外，还常响应环境变化发挥额外调控作用。然而，目前学界对母体经历如何转化为调控子代发育的分子信号的相关机制仍知之甚少。此类信号之一可能是沉积于成熟卵母细胞中的母体RNA转录本：信使RNA（messenger RNA，mRNA）与微小RNA（microRNA，miRNA）。这些转录本调控所有动物的早期发育阶段，但在多数昆虫类群中相关研究仍较为匮乏。本研究以苜蓿切叶蜂为研究对象，探究了雌性个体内部（身体状况）与外部（季节时间）环境条件对其成熟卵母细胞及24小时龄卵（24h卵）中母体RNA的影响。本研究通过基因表达（gene expression）分析与加权基因共表达网络分析（Weighted Gene Co-expression Network Analysis，WGCNA）发现，雌性个体可响应身体状况不佳以及季末伴随的日照时长缩短，调整沉积于成熟卵母细胞中与蛋白质磷酸化、转录调控及核酸酶活性相关的mRNA数量；但相较于身体状况，季节时间对mRNA数量的调控幅度更大。此外，雌性个体仅会响应季节变化调整miRNA的沉积量，不会因身体状况产生此类调整。在已完成母源-合子转换（maternal-to-zygotic transition，MZT）的24h卵中，我们未观测到母体RNA因身体状况或季节时间产生显著变化。本研究结果表明，雌性个体可通过调整为子代提供的RNA转录本，以响应内外环境信号调控子代发育；因此，母体RNA的变异可能在响应环境变化、调控子代表型方面发挥重要作用。