Bacillus subtilis sigma factor sigma 29 is the product of the sporulation-essential gene spoIIG.

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Abstract
Evidence is presented that the sporulation-essential locus spoIIG codes for both .sigma.29 and a structurally related protein, P31. This demonstrates that at least 1 specific B. subtilis RNA polymerase binding protein provides a critical function in endospore formation. spoIIG-specific RNA is present in B. subtilis cultures that are synthesizing P31 and .sigma.29 and is absent in those that are not. A monoclonal antibody specific for an antigenic determinant on P31/.sigma.29 detected crossreacting proteins (P25/P21) but not P31 or .sigma.29 in a Spo- B. subtilis strain with a mutation at the spoIIG locus (spoIIG41). The appearance of P25 and P21 occurs in this mutant at a time when P31 and .sigma.29 would normally appear and suggests that they are homologous proteins. Transformation of the spoIIG41 strain with plasmid DNA carrying the structural gene for spoIIG complements the Spo- phenotype and results in the synthesis of P31, .sigma.29, P25 and P21 at the appropriate times during sporulation. In Escherichia coli, the cloned spoIIG sequence encoded a protein that reacted with the anti-P31/.sigma.29 monoclonal antibody and had the electrophoretic mobility of authentic P31.