A multifunctional polyketide synthase in nematodes produces divergent families of signaling molecules that control different developmental arrests

Abstract

To improve their chances of reproductive success, nematodes not only must arrest their development in response to adverse growth conditions but also must quickly recover if conditions improve. A polyketide synthase (PKS)-nonribosomal peptide synthetase (NRPS) hybrid assembly line that is expressed in the canal-associated neurons (CANs) of Caenorhabditis elegans promotes recovery from starvation-induced larval arrest. Here, we show that in the predatory nematode Pristionchus pacificus this assembly line produces a suite of secondary metabolites, including a family of hybrid polyketide-nonribosomal peptides known as the nemamides, the related nemaketides, and a family of ascarylose-modified polyketides named ascarenes. Depending on the starter unit that is loaded onto the PKS, the assembly line can produce dramatically different downstream products. Whereas the nemamides promote recovery from starvation-induced larval arrest, the ascarenes inhibit development of the dauer larval stage and promote recovery. This dichotomy suggests that the PKS-NRPS megasynthetase serves as a signaling hub in the CANs, controlling multiple developmental events. The PKS-NRPS assembly line is highly conserved across many nematode species, and identification of these chemical signals will help to elucidate the signaling pathways that control development in the worm and lead to novel anthelmintics.