Epigenomics: A Way Forward from Classical Approach

Epigenomics is developing expeditiously in insect research wherein, without involvement of changes in DNA sequence, the adaptations to environmental changes are addressed. Besides, when there are endogenous and environmental stimuli, epigenetics is involved in the reprogramming of gene expression. Epigenetic changes occur through the presence of pathogens, parasites, harmful chemicals, varied temperature, humidity, and other stress factors. Epigenetic modifications are strongly evident in causing reprogramming of transcriptional process and known to be passed from parents to offspring. DNA methylation, histone acetylation, and histone methylation are the major epigenomic mechanisms added to which there are posttranscriptional gene regulation heritable mechanisms, i.e., the synthesis of noncoding microRNAs (miRNAs) known to bind corresponding messenger RNAs (mRNAs) and degrade its activity, thereby inhibiting translation. In addition to miRNAs, long noncoding RNAs (lncRNAs; >200 nucleotides in length) play an important role in regulating complex biological processes and also during stress through epigenetic control. Emerging evidences have revealed a key role of lncRNAs in regulating immunological functions and autoimmunity. Recent discoveries have shown that different epigenetic pathways along with microRNAs (miRNAs) form regulatory circuit involving epigenetics and miRNA which provides strong biological insights into gene-regulatory mechanism(s) underlying a variety of diseases. Collectively, progressing inputs by many studies on epigenetics, questioning whether the occurrence of phenotypic plasticity is through the role of epigenetics, are dealt, and the overall advancement in the field of epigenomics as a new avenue to unravel the silkworm biological system complexity under stressful environmental conditions, genetic diversity, heterosis, and impact on productivity information will be purveyed in this chapter.