Characterization of a male-killing virus and its mode of action in Homona magnanima

许多无脊椎动物物种中都记录了母系遗传的雌性性别比例。造成这种性别比例偏差的原因之一是杀戮男性。也就是说，只有雄性会死亡。在大多数物种中，雄性杀戮发生在胚胎阶段（早期雄性杀戮），并且与细胞质细菌有关。然而，东方茶树（Homona magnanima）是雄性在幼虫或蛹阶段死亡的少数物种之一，因此是晚期雄性捕杀的一个例子。本研究对一种晚期雄性致死品系（LMK）的大体形态和组织病理学进行了研究，并研究了该药剂在天然种群中的时空动态，并部分纯化了导致晚期雄性致死的药剂。大多数LMK雄性幼虫在末龄或蛹期死亡，死亡的雄性幼虫表现出雄性致死的特征性体征和症状。雄性LMK幼虫的体色在蜕变成五龄后4天开始发生变化，并变得越来越不透明的白色。雄性 LMK 幼虫的重量明显低于正常品系 (NSR) 雄性。雄性LMK幼虫的中肠细胞在最后一次蜕皮后7天以颗粒形式排出到管腔中，并在死亡前落入管腔中。雄性LMK幼虫的脂肪体细胞质中含有大的脂肪颗粒，但成为肿瘤样细胞团，最终与表皮细胞融合。为了鉴定晚期雄性杀伤剂，我们通过蔗糖梯度超速离心从雄性LMK幼虫中纯化了致病剂。注射实验表明纯化级分含有晚期雄性杀伤剂，电镜观察表明纯化级分具有直径10-15 nm的等轴颗粒。纯化级分中的核酸被 RNase A 降解，但不被 DNase I 降解，这表明纯化级分中的核酸是 RNA 而不是 DNA。从纯化的级分中鉴定出 LMK 特异性的两个 RNA 序列 MK1068 和 MK1241。 BLAST 研究表明，它们的核苷酸和推导的氨基酸序列与任何其他已知序列都不匹配。这些结果表明，H. magnanima 的雄性死亡可能是由一种新的 RNA 病毒引起的。这种RNA病毒是从宫崎县、岐阜县、静冈县、埼玉县和茨城县收集的H. magnanima幼虫中检测到的。较少的

Maternally inherited female-biased sex ratios have been documented in many invertebrate species. One cause of such biased sex ratios is male-killing ; that is, only males die. In most species, male-killing occurs during embryonic stages (early male-killing) and is associated with cytoplasmic bacteria. However, the oriental tea tortrix, Homona magnanima, is one of the few species in which male death occurs in the larval or pupal stage, and is thus an example of late male-killing. In this study, we examined the gross morphology and histopathology of a late male-killing strain (LMK) of H. magnanima larvae, and spatial and temporal dynamics of the agent in natural populations of H. magnanima, and partially purified the agent causing late male-killing in H. magnanima.Most male LMK larvae died during the last instar or pupal stage, and dead male larvae showed characteristic signs and symptoms of male-killing. The body color of male LMK larvae started to change 4 days after molting into the f … More ifth instar and became increasingly opaque white. Male LMK larvae weighed significantly less than normal strain (NSR) males. Midgut cells of male LMK larvae were discharged into the lumen as granules at 7 days after the final molt, and dropped into the lumen just before death. The fat body of male LMK larvae contained large fat granules in the cytoplasm but became a tumorlike cell mass that finally fused with the epidermal cells.To identify the late male-killing agent, we purified a causal agent from male LMK larvae by sucrose gradient ultracentrifugation. Injection experiment revealed that the purified fraction contained the late male-killing agent, and electron microscopy showed that the purified fraction has isometric particles of 10-15 nm in diameter. Nucleic acids in the purified fraction were degraded by RNase A but not by DNase I, which suggests that nucleic acids in the purified fraction were RNAs but not DNAs. LMK specific two RNA sequences, MK1068 and MK1241, were identified from the purified fraction. A BLAST research revealed that their nucleotide and deduced amino acid sequences did not match any other known sequences. These results suggested that male-killing in H. magnanima may be caused by a new RNA virus. This RNA virus was detected from H. magnanima larvae collected in Miyazaki, Gifu, Shizuoka, Saitama and Ibaragi Prefectures. Less