麻省理工學(xué)院的一組研究者通過(guò)對(duì)162株線蟲進(jìn)行研究,，發(fā)現(xiàn)了線蟲逃避有害細(xì)菌的基因機(jī)制，其結(jié)果近日發(fā)表在《自然》(Nature)雜志上,。
在實(shí)驗(yàn)中，研究者將162株線蟲分別置于盛有銅綠假單胞桿菌菌落的盤子中，然后觀察這些線蟲的行為,。一開始，線蟲都設(shè)法接近菌落,，而24小時(shí)后再次觀察時(shí),，他們發(fā)現(xiàn)大部分線蟲都遠(yuǎn)離了菌落，而且這些線蟲都略有增大,，這表明這些線蟲都曾吃過(guò)菌落,，而當(dāng)它們知道其危害后，再也沒有吃過(guò)第二口,。然而,，在研究人員第二次觀察時(shí),，仍有一株線蟲在吃菌落,，其中的大部分線蟲都已經(jīng)死亡,。
為了研究清楚這些線蟲逃避有害細(xì)菌的機(jī)制，研究者將不同線蟲株的基因組進(jìn)行了對(duì)比,，他們發(fā)現(xiàn)仍在食用細(xì)菌的線蟲HECW1基因發(fā)生了突變,，該基因在線蟲的神經(jīng)信號(hào)傳遞中起作用,。線蟲有2個(gè)感覺神經(jīng)元基因中包含HECW1基因,。隨后,，研究者用激光將那些逃避較慢的線蟲的這2個(gè)神經(jīng)元破壞,，這時(shí)這些線蟲又向菌落爬去。這表明HECW1基因在線蟲對(duì)銅綠假單胞桿菌的逃避中起作用,。
研究者指出，這種機(jī)制或許只能被銅綠假單胞桿菌激發(fā),，而那些逃避較慢的線蟲,，或許在其生存環(huán)境中不會(huì)接觸到銅綠假單胞桿菌,，因此它們不需要逃避這種細(xì)菌。這對(duì)于線蟲來(lái)說(shuō)或許算是好事,，因?yàn)榫€蟲僅有302個(gè)神經(jīng)元來(lái)應(yīng)對(duì)環(huán)境中的各種情況,，它們對(duì)食物的要求不能過(guò)于苛刻,，否則它們就得挨餓。
劍橋大學(xué)的神經(jīng)學(xué)家馬里奧·波諾稱,，該研究很好地證實(shí)了線蟲可以作為行為學(xué)的基因基礎(chǔ)的研究模型，雖然人類的神經(jīng)元數(shù)目遠(yuǎn)遠(yuǎn)多于線蟲,，但二者的部分神經(jīng)通路是類似的,。（生物谷bioon.com）
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Natural polymorphisms in C. elegans HECW-1 E3 ligase affect pathogen avoidance behaviour
Howard C. Chang，Jennifer Paek & Dennis H. Kim
Heritable variation in behavioural traits generally has a complex genetic basis1, and thus naturally occurring polymorphisms that influence behaviour have been defined only in rare instances2, 3. The isolation of wild strains of Caenorhabditis elegans has facilitated the study of natural genetic variation in this species4 and provided insights into its diverse microbial ecology5. C. elegans responds to bacterial infection with conserved innate immune responses6, 7, 8 and, although lacking the immunological memory of vertebrate adaptive immunity, shows an aversive learning response to pathogenic bacteria9. Here, we report the molecular characterization of naturally occurring coding polymorphisms in a C. elegans gene encoding a conserved HECT domain-containing E3 ubiquitin ligase, HECW-1. We show that two distinct polymorphisms in neighbouring residues of HECW-1 each affect C. elegans behavioural avoidance of a lawn of Pseudomonas aeruginosa. Neuron-specific rescue and ablation experiments and genetic interaction analysis indicate that HECW-1 functions in a pair of sensory neurons to inhibit P. aeruginosa lawn avoidance behaviour through inhibition of the neuropeptide receptor NPR-1 (ref. 10), which we have previously shown promotes P. aeruginosa lawn avoidance behaviour11. Our data establish a molecular basis for natural variation in a C. elegans behaviour that may undergo adaptive changes in response to microbial pathogens.
