Department of Biology, California State University, Northridge, Northridge, CA 91330-8303, USA.
Department of Microbiology, Immunology & Molecular Genetics and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA.
Genetics. 2021 Jun 24;218(2). doi: 10.1093/genetics/iyab071.
Developmental and behavioral plasticity allow animals to prioritize alternative genetic programs during fluctuating environments. Behavioral remodeling may be acute in animals that interact with host organisms, since reproductive adults and the developmentally arrested larvae often have different ethological needs for chemical stimuli. To understand the genes that coordinate the development and host-seeking behavior, we used the entomophilic nematode Pristionchus pacificus to characterize dauer-constitutive mutants (Daf-c) that inappropriately enter developmental diapause to become dauer larvae. We found two Daf-c loci with dauer-constitutive and cuticle exsheathment phenotypes that can be rescued by the feeding of Δ7-dafachronic acid, and that are dependent on the conserved canonical steroid hormone receptor Ppa-DAF-12. Specifically at one locus, deletions in the sole hydroxysteroid dehydrogenase (HSD) in P. pacificus resulted in Daf-c phenotypes. Ppa-hsd-2 is expressed in the canal-associated neurons (CANs) and excretory cells whose homologous cells in Caenorhabditis elegans are not known to be involved in the dauer decision. While in wildtype only dauer larvae are attracted to host odors, hsd-2 mutant adults show enhanced attraction to the host beetle pheromone, along with ectopic activation of a marker for putative olfactory neurons, Ppa-odr-3. Surprisingly, this enhanced odor attraction acts independently of the Δ7-DA/DAF-12 module, suggesting that Ppa-HSD-2 may be responsible for several steroid hormone products involved in coordinating the dauer decision and host-seeking behavior in P. pacificus.
发育和行为可塑性使动物能够在环境波动时优先选择替代的遗传程序。与宿主生物相互作用的动物的行为重塑可能是急性的，因为生殖成体和发育停滞的幼虫通常对化学刺激有不同的行为需求。为了了解协调发育和宿主觅取行为的基因，我们使用嗜虫线虫秀丽隐杆线虫来表征 dauer 组成型突变体（Daf-c），这些突变体不适当地进入发育休眠状态成为 dauer 幼虫。我们发现了两个 Daf-c 基因座，具有 dauer 组成型和角质层蜕皮表型，可以通过喂食 Δ7-dafachronic acid 来挽救，并且依赖于保守的经典类固醇激素受体 Ppa-DAF-12。具体来说，在一个基因座上，秀丽隐杆线虫中唯一的羟甾脱氢酶（HSD）缺失导致 Daf-c 表型。Ppa-hsd-2 在与管相关的神经元（CANs）和排泄细胞中表达，而秀丽隐杆线虫中同源细胞是否参与 dauer 决策尚不清楚。虽然在野生型中只有 dauer 幼虫对宿主气味有吸引力，但 hsd-2 突变体成虫对宿主甲虫信息素的吸引力增强，同时对假定嗅觉神经元的标记物 Ppa-odr-3 也发生了异位激活。令人惊讶的是，这种增强的气味吸引力独立于 Δ7-DA/DAF-12 模块起作用，表明 Ppa-HSD-2 可能负责协调 dauer 决策和宿主觅取行为的几种类固醇激素产物在秀丽隐杆线虫中的作用。
