LAUSR

Our recent paper in mBio (1) prompted Richard Losick to criticize our hypothesis for Ric protein function (2, 3). Although his concerns are not with this recent paper, R. Losick prefers a different hypothesis for Ric protein function (4, 5). However, our respective models are not mutually exclusive. There is no evidence showing that our model is wrong, and there is evidence supporting our model as well as the compatible one proposed by R. Losick. Our starting point was with the observations that inactivation of ricA ( ymcA ), ricF ( ylbF ), or ricT ( yaaT ) prevented biofilm formation, genetic competence, and sporulation (6–8), all processes requiring the phosphorylation of Spo0A. The use of reporter constructs confirmed that the activation of Spo0A was dependent on the Ric proteins, while alleles of spo0A that suppress defects in the phosphorelay bypassed the ric requirements for transcription of Spo0A-P-dependent genes (2, 9). Similar results had already been independently reported for RicT (7). Importantly, a purified complex of the three Ric proteins stimulated the phosphorelay two- to threefold in vitro (2), so we proposed this direct action as the role of the Ric proteins. The Losick lab then published papers proposing that these proteins were directly involved in RNA processing (4, 5). Since then we have acknowledged repeatedly that the Ric proteins are required in vivo for RNA processing events (1, 3, 9), and we have ourselves confirmed and extended this observation (1). Furthermore, we showed explicitly that the phosphorelay effect was only part of the Ric story, and we even proposed that the Losick hypothesis could explain …