Department of Biology, California State University Northridge, Northridge, California, United States of America.
PLoS One. 2012;7(4):e34464. doi: 10.1371/journal.pone.0034464. Epub 2012 Apr 26.
The genetic tractability and the species-specific association with beetles make the nematode Pristionchus pacificus an exciting emerging model organism for comparative studies in development and behavior. P. pacificus differs from Caenorhabditis elegans (a bacterial feeder) by its buccal teeth and the lack of pharyngeal grinders, but almost nothing is known about which genes coordinate P. pacificus feeding behaviors, such as pharyngeal pumping rate, locomotion, and fat storage.
METHODOLOGY/PRINCIPAL FINDINGS: We analyzed P. pacificus pharyngeal pumping rate and locomotion behavior on and off food, as well as on different species of bacteria (Escherichia coli, Bacillus subtilis, and Caulobacter crescentus). We found that the cGMP-dependent protein kinase G (PKG) Ppa-EGL-4 in P. pacificus plays an important role in regulating the pumping rate, mouth form dimorphism, the duration of forward locomotion, and the amount of fat stored in intestine. In addition, Ppa-EGL-4 interacts with Ppa-OBI-1, a recently identified protein involved in chemosensation, to influence feeding and locomotion behavior. We also found that C. crescentus NA1000 increased pharyngeal pumping as well as fat storage in P. pacificus.
The PKG EGL-4 has conserved functions in regulating feeding behavior in both C. elegans and P. pacificus nematodes. The Ppa-EGL-4 also has been co-opted during evolution to regulate P. pacificus mouth form dimorphism that indirectly affect pharyngeal pumping rate. Specifically, the lack of Ppa-EGL-4 function increases pharyngeal pumping, time spent in forward locomotion, and fat storage, in part as a result of higher food intake. Ppa-OBI-1 functions upstream or parallel to Ppa-EGL-4. The beetle-associated omnivorous P. pacificus respond differently to changes in food state and food quality compared to the exclusively bacteriovorous C. elegans.
秀丽隐杆线虫（Pristionchus pacificus）具有遗传操作的便利性和与甲虫的物种特异性关联，使其成为发展和行为比较研究的一个令人兴奋的新兴模式生物。与以细菌为食的秀丽隐杆线虫（Caenorhabditis elegans）不同，太平洋真涡虫（Pristionchus pacificus）具有颊齿和缺乏咽磨，但人们几乎不知道哪些基因协调太平洋真涡虫的摄食行为，如咽泵速率、运动和脂肪储存。
方法/主要发现：我们分析了太平洋真涡虫在有食物和无食物时的咽泵速率和运动行为，以及不同种类的细菌（大肠杆菌、枯草芽孢杆菌和新月柄杆菌）。我们发现，太平洋真涡虫中的环鸟苷酸依赖性蛋白激酶 G（PKG）Ppa-EGL-4 在调节泵速、口型二态性、向前运动的持续时间以及肠道中储存的脂肪量方面发挥着重要作用。此外，Ppa-EGL-4 与最近发现的参与化学感觉的 Ppa-OBI-1 相互作用，影响摄食和运动行为。我们还发现，新月柄杆菌 NA1000 增加了太平洋真涡虫的咽泵速率和脂肪储存。
PKG EGL-4 在调节秀丽线虫和太平洋真涡虫的摄食行为方面具有保守功能。Ppa-EGL-4 也在进化过程中被重新利用，调节太平洋真涡虫的口型二态性，间接影响咽泵速率。具体来说，缺乏 Ppa-EGL-4 功能会增加咽泵速率、向前运动的时间和脂肪储存，部分原因是食物摄入量增加。Ppa-OBI-1 功能在上游或与 Ppa-EGL-4 平行。与专门以细菌为食的秀丽线虫相比，与甲虫相关的杂食性太平洋真涡虫对食物状态和食物质量的变化反应不同。
