Transcriptomic screen to identify genes regulated by IP3R in Drosophila third-instar larval nervous system. Transcriptomic screen to identify genes regulated by IP3R in Drosophila third-instar larval nervous system

Organisms need to co-ordinate growth with development particularly in the context of nutrient availability. Thus, multiple ways have evolved to survive extrinsic nutrient deprivation during development. In the holometabolous insect Drosophila, growth occurs during larval development. Larvae are therefore critically dependent on nutritional inputs for pupariation. Post critical weight however, they pupariate even when starved. How nutrient availability is coupled to the internal metabolic state for the decision to pupariate in not well understood and needs better understanding. Wild type larvae, when subjected to nutrient deprivation as mid-third instar larvae, pupariate and also emerge as adults, even though smaller than normally fed ones (Jayakumar et al., 2016; Megha and Hasan, 2017). A recent study (Jayakumar et al., 2016) identified a neuronal circuit that enables wild-type larvae to survive protein deprivation and pupariate. IP3R function in a subset of glutamatergic neurons is a crucial part of the circuit. However, the cellular role of IP3R in these neurons is not understood. In Drosophila neurons, the IP3R causes and facilitates store-operated calcium entry (Chakraborty et al., 2016; Venkiteswaran and Hasan, 2009). Thus it is likely, that the IP3R also regulates expression of genes that regulate this phenomenon. In this study, we have compared the gene expression profiles of control and itpr knockdown larval brains to identify genes that act downstream of the IP3R to regulate pupariation under nutrition stress. Overall design: mRNA sequencing from three biological relicates of control and two biological replicates of IP3R knockdown third instar larval brains

生物有机体需要协调生长与发育，尤其在营养可获得性的背景下。因此，演化出多种策略以在发育过程中耐受外界营养剥夺。在完全变态昆虫果蝇（Drosophila）中，生长阶段发生于幼虫发育期，因此幼虫能否成功化蛹高度依赖营养摄入。不过，当幼虫达到临界体重后，即便处于饥饿状态也仍可化蛹。目前，营养可获得性如何与机体内部代谢状态耦合，以调控化蛹决策的机制仍未被充分阐明，有待进一步研究。野生型幼虫若在三龄中期遭受营养剥夺，仍可完成化蛹并羽化成为成虫，尽管其体型较正常喂食的幼虫更小（Jayakumar等，2016；Megha和Hasan，2017）。近期一项研究（Jayakumar等，2016）鉴定出一条可帮助野生型幼虫耐受蛋白质剥夺并完成化蛹的神经环路，其中三磷酸肌醇受体（IP3R）在一类谷氨酸能神经元中的功能是该环路的关键一环。然而，IP3R在这些神经元中的细胞层面功能仍不明确。在果蝇神经元中，IP3R可诱发并介导钙池操纵性钙内流（store-operated calcium entry）（Chakraborty等，2016；Venkiteswaran和Hasan，2009）。因此，IP3R大概率也可调控参与该过程的基因的表达。本研究中，我们对对照组及itpr基因敲低的三龄幼虫脑部进行了基因表达谱对比分析，以鉴定出在营养胁迫下介导IP3R下游调控化蛹过程的基因。整体实验设计：对3个生物学重复的对照组三龄幼虫脑部，以及2个生物学重复的IP3R敲低组三龄幼虫脑部进行mRNA测序。