Long-term imaging reveals behavioral plasticity during C. elegans dauer exit.

During their lifetime, animals must adapt their behavior to survive in changing environments. This ability requires the nervous system to adjust through dynamic expression of neurotransmitters and receptors but also through growth, spatial reorganization and connectivity while integrating external stimuli. For instance, despite having a fixed neuronal cell lineage, the nematode Caenorhabditis elegans’ nervous system remains plastic throughout its development. Here, we focus on a specific example of nervous system plasticity, the C. elegans dauer exit decision. Under unfavorable conditions, larvae will enter the non-feeding and non-reproductive dauer stage and adapt their behavior to cope with a new environment. Upon improved conditions, this stress resistant developmental stage is actively reversed to resume reproductive development. However, how different environmental stimuli regulate the exit decision mechanism and thereby drive the larva’s behavioral change is unknown. To fill this gap, we developed a new open hardware method for long-term imaging (12h) of C.elegans larvae. We identified dauer-specific behavioral motifs and characterized the behavioral trajectory of dauer exit in different environments to identify key decision points. Combining long-term behavioral imaging with transcriptomics, we find that bacterial ingestion triggers a change in neuropeptide gene expression to establish post-dauer behavior. Taken together, we show how a developing nervous system can robustly integrate environmental changes, activate a developmental switch and adapt the organism’s behavior to a new environment. Transcriptional analysis at 4 different time points (0h, 3h, 6h, 9h) during dauer exit in 2 different environments (with bacteria & no bacteria)

动物在其生命周期中，必须调整自身行为以在多变的环境中存活。这一能力要求神经系统通过神经递质与受体的动态表达、生长、空间重构与连接重塑进行调节，同时整合外部刺激信号。例如，尽管拥有固定的神经元细胞谱系，秀丽隐杆线虫（Caenorhabditis elegans）的神经系统在整个发育过程中仍保持可塑性。本研究聚焦于神经系统可塑性的一个典型案例：秀丽隐杆线虫的持久态（dauer）退出决策。当环境条件不利时，幼虫会进入不进食、不繁殖的持久态阶段，并调整自身行为以适应新环境。当环境条件改善后，这一具有抗逆性的发育阶段会被主动逆转，重新开启生殖发育进程。然而，目前尚不清楚不同的环境刺激如何调控退出决策机制，进而驱动幼虫的行为改变。为填补这一研究空白，我们开发了一种全新的开放式硬件方法，可对秀丽隐杆线虫幼虫进行长达12小时的长期成像。我们鉴定出了持久态特异性的行为特征模式，并刻画了不同环境下持久态退出的行为轨迹，以确定关键决策节点。通过将长期行为成像与转录组学（transcriptomics）分析相结合，我们发现细菌摄食会触发神经肽基因表达的改变，从而建立持久态退出后的行为模式。综上，本研究阐明了发育中的神经系统如何鲁棒地整合环境变化、激活发育开关，并使生物体的行为适应新环境。本研究在两种不同环境（有细菌与无细菌）下，于持久态退出过程中的4个时间点（0h、3h、6h、9h）开展了转录组分析。