The ambiguous source of vitellogenin: either pharyngeal glands or seam cells, or both?

During the life-cycle of plant-parasitic nematodes the second-stage juvenile develops within the egg and is bathed in vitelline fluid that contains a number of proteins one of which is vitellogenin, the precursor to vitellin. This protein is abundant in the egg but its origin and function is poorly understood. In Caenorhabditis elegans six genes have been identified that are expressed in the intestine and the protein is then transported through the body cavity to the ovary where it is deposited in the yolk of the egg. These vit proteins, in C. elegans are thought to be responsible during embryogenesis for the transport of nutrients and are important in the development of progeny. However, they also possibly have a protective environmental role against oxidative stress and microbial infection. Here using three different antibodies, two raised to proteins present in vitellin fluid and a third raised to a synthetic peptide of vitellogenin common to the cyst nematodes Globodera pallida, G. rostochiensis and Heterodera schachtii, we characterise the proteins by Western-blot analysis and immunolocalisation. One of the antibodies UH-VitA recognised a protein with an 86% similarity to vitellogenin proteins that was localised to the seam cells of the J2 of H. schachtii. Undertaking a literature search we identified a manuscript reporting vitellogenin proteins in C. elegans and Oscheius tipulae also present the proteome of the pharyngeal glands of Meloidogyne incognita (Wang et al., 2012; doi.org/10.1016/j.ijpara.2012.10.008). Our work is the first research with a reference to seam cells in the plant-parasitic nematode literature; however, the functional role and origin of vitellogenin in plant-parasitic nematodes remains ambiguous.