Identification of methyltransferase and demethylase genes and their expression profiling under biotic and abiotic stress in pigeon pea (Cajanus cajan [L.] Millspaugh)

The methylation- demethylation dynamics of RNA plays major roles in different biological functions, including stress responses, in plants. m⁶A methylation in RNA is orchestrated by a coordinated function of methyl transferases (writers) and demethylases (Erasers). Genome-wide analysis of genes involved in methylation and demethylation was performed in pigeon pea. Blast search, using Arabidopsis gene sequences, resulted in the identification of two methylation genes (<i>CcMTA70</i>, <i>CcMTB70</i>), two genes encoding adaptor proteins for methylation (<i>CcFIPA</i> and <i>CcFIPB</i>) and 10 demethylase (ALKBH) genes (<i>CcALKBH1A</i>, <i>CcALKBH1B</i>, <i>CcALKBH1C</i>, <i>CcALKBH2</i>, <i>CcALKBH8</i>, <i>CcALKBH8A</i>, <i>CcALKBH8B</i>, <i>CcALKBH9</i>, <i>CcALKBH10A</i> and <i>CcALKBH10B</i>) in the pigeon pea genome. The identified genes were analyzed through phylogenetic relationship, chromosomal position, gene structure, conserved motif, domain and subcellular location prediction etc. These structural analyses resulted in categorization of MTs and FIPs into one group, i.e.<i>, CcMTA/B</i> and <i>CcFIPA/B</i>, respectively; and ALKBHs into four groups, viz. <i>CcALKBH1/</i>2, <i>CcALKBH</i>8, <i>CcALKBH</i>9 and <i>CcALKBH</i>10. Relative expression analysis of the identified genes in various tissues at different developmental stages revealed the highest level of expression in leaf and the least in root. <i>CcMT</i>s and <i>CcFIP</i>s had similar patterns of expression, and <i>CcALKBH10B</i> demonstrated the highest and <i>CcALKBH2</i> the lowest level of expression in all the tissues analyzed. <i>CcALKBH8</i> showed the highest induction in expression upon exposure to heat stress, and <i>CcALKBH10B</i> demonstrated the highest level of induction in expression during drought, salt and biotic (<i>Helicoverpa armigera</i> infestation) stresses. The present study would pave the way for detailed molecular characterization of m⁶A methylation in pigeon pea and its involvement in stress regulation.