Schematic diagram of the transcriptional patterns of fasting-induced genes in response to fasting. (A) A cartoon to show the rationales of how the MONITTR system can be used to examine the functions of NHR-49 and HLH-30 in inducing the expression of endogenous icl-1 and adh-1 upon fasting. (B) At the single-allele level, the duration of burst and pause in the transcription process of fasting-induced genes are key determinants. For icl-1, The single duration and total duration of burst(s) are longer in WT than in the nhr-49 and hlh-30 mutant animals, while the single duration and total duration of pause are shorter in these two mutant strains. At the level of individual cells and tissues, NHR-49 and HLH-30 act as the key transcriptional factors to up-regulate the transcription of fasting-induced genes by turning on more alleles and more cells in response to fasting.