Kesarwani, V.; Kumar, A.; Sharma, A.; Gupta, S.; Shankar, R.

Compared to other nucleotides, the cytosines stand as the most expressive one for gene regulation in plants due to its status as methylation-based epigenetic switch. Methylation of some of these cytosines may have higher impact on the downstream genes, making them critical ones. To this date not much has been done to decipher the criticality of such cytosines. Understanding them may open door-ways for minimal interventions led modification and control of gene expression. This is one such pioneering step in decoding the critical 'C's where a large volume of bisulfite and RNA-seq data, including 232 WGBS and 260 corresponding RNA-seq datasets from A. thaliana and rice, have been utilized to decode criticality of cytosines in plants. Using a deep learning system, strong relationship was established between the methylation states of cytosines in contextual manner with respect to the downstream genes expression levels. Using the same system, all the 2kb upstream regions for Arabidopsis and rice genes have been annotated. The developed approach has been shown to be a universal one and may be used to annotate other plant genomes to identify critical cytosines. The developed resource and the deep-learning system to decode criticality have been made publicly available as CritiCal-C portal, which is poised to accelerate the field of plant epigenomics and regulatory studies.