Methyltransferase which methylates the carbon-5 position of cytosine 2982 to 5-methylcytosine (m5C2982) in 26S rRNA (PubMed:33289480, PubMed:33283887). May play a role in the translation of leucine and proline codons (Probable). May be required for the translation of specific mRNAs such as mRNAs involved in gonad development, collagen production and cuticle integrity (PubMed:33289480). Plays a role in ensuring the correct localization of the germline-specific protein gld-1 during development (PubMed:33289480). Not required for pre-rRNA processing, the production of mature 5S, 5.8S, 18S or 26S rRNAs or global translation (PubMed:33289480). Plays a role in positively regulating fertility (PubMed:33283887). a cytidine in 26S rRNA + S-adenosyl-L-methionine = a 5-methylcytidine in 26S rRNA + H(+) + S-adenosyl-L-homocysteine Expression increases during the larval stages to adulthood. RNAi-mediated knockdown in L1 larvae results in sterility (PubMed:33283887). RNAi-mediated knockdown in adults results in reduced egg-laying (PubMed:33289480). RNAi-mediated knockdown from day 0 of adulthood or in the germline does not affect lifespan (PubMed:33289480). RNAi-mediated knockdown in somatic tissues reduces lifespan by 10% and reduces body length and results in morphological defects in the gonad leading to the production of no oocytes (PubMed:33289480). RNAi-mediated knockdown increases resistance to heat stress and increases the speed of locomotion (PubMed:33289480). RNAi-mediated knockdown disrupts the localization of the germline-specific protein gld-1, results in collagen deposition and increases cuticle permeability (PubMed:33289480). RNAi-mediated knockdown reduces the methylation of cytosine to 5-methylcytosine (m5C) in 26S rRNA (PubMed:33289480). RNAi-mediated knockdown does not affect the methylation of cytosine 2381 to 5-methylcytosine (m5C2381) in 26S rRNA (PubMed:33289480). Belongs to the class I-like SAM-binding methyltransferase superfamily. RsmB/NOP family.