Department of Biology, Colby College, 5700 Mayflower Hill, Waterville, ME 04901, USA.
Integr Comp Biol. 2022 Oct 29;62(4):1042-1055. doi: 10.1093/icb/icac092.
Polyphenism allows organisms to respond to varying environmental conditions by adopting alternative collections of morphological traits, often leading to different reproductive strategies. In many insects, polyphenism affecting the development of flight trades dispersal ability for increased fecundity. The soapberry bug Jadera haematoloma (Hemiptera: Rhopalidae) exhibits wing polyphenism in response to juvenile nutritional resources and cohort density. Development of full-length wings and flight-capable thoracic muscles occurs more frequently in cohorts raised under low food density conditions, and these features are correlated to reduced female fecundity. Soapberry bugs represent an example of polyphenic dispersal-fecundity trade-off. Short-wing development is not sex-limited, and morphs can also differ in male fertility. We have previously shown, via a candidate gene approach, that manipulation of insulin signaling can alter the threshold for nutritional response and that changes in the activity of this pathway underlie, at least in part, differences in the polyphenic thresholds in different host-adapted populations of J. haematoloma. We now expand the examination of this system using transcriptome sequencing across a multidimensional matrix of life stage, tissue, sex, food density, and host population. We also examine the use of wing and thorax shape as factors modeling gene expression. In addition to insulin signaling, we find that components of the TOR, Hippo, Toll, and estrogen-related receptor pathways are differentially expressed in the thorax of polyphenic morphs. The transcription factor Sox14 was one of the few genes differentially expressed in the gonads of morphs, being up-regulated in ovaries. We identify two transcription factors as potential mediators of morph-specific male fertility differences. We also find that bugs respond to nutrient limitation with expression of genes linked to cuticle structure and spermatogenesis. These findings provide a broad perspective from which to view this nutrition-dependent polyphenism.
多态性使生物体能够通过采用不同的形态特征集合来应对不同的环境条件，通常导致不同的繁殖策略。在许多昆虫中，影响飞行贸易的多态性会影响扩散能力和增加繁殖力。皂角虫 Jadera haematoloma（半翅目：Rhopalidae）对幼年营养资源和群体密度做出反应，表现出翅膀多态性。在食物密度低的条件下，发育出全长翅膀和具有飞行能力的胸部肌肉的比例更高，而这些特征与降低的雌性繁殖力相关。皂角虫代表了多态性扩散-繁殖力权衡的一个例子。短翅发育不是性别限制的，并且形态也可以在雄性生育力上有所不同。我们之前通过候选基因方法表明，胰岛素信号的操纵可以改变营养反应的阈值，并且该途径活性的变化至少部分地解释了不同宿主适应种群中多态性阈值的差异。我们现在使用转录组测序技术在多维生命阶段、组织、性别、食物密度和宿主种群矩阵中扩展了对该系统的检查。我们还研究了翅膀和胸部形状作为模拟基因表达的因素。除了胰岛素信号外，我们还发现 TOR、Hippo、Toll 和雌激素相关受体途径的成分在多态性形态的胸部中差异表达。转录因子 Sox14 是在形态的生殖腺中差异表达的少数基因之一，在卵巢中上调。我们确定了两个转录因子作为潜在的形态特异性雄性生育力差异的介导因子。我们还发现，当昆虫受到营养限制时，会表达与表皮结构和精子发生相关的基因。这些发现为研究这种依赖营养的多态性提供了一个广泛的视角。
