Cyst Nematode Single-Cell Omics
By Thomas Baum, professor of plant pathology, entomology and microbiology, ISU
Project Summary
The soybean cyst nematode (SCN) is the most serious pathogen problem of US soybean production. This nematode is an obligate parasite that becomes sedentary inside the soybean root and induces hundreds of soybean cells to completely change their morphology and function to form a novel plant organ, the syncytium, which nourishes the parasite.
Interestingly, during SCN infection the cells most intricately involved in parasitism, both in the nematode and the soybean plant, multiply their DNA content. In the nematode, three gland cells that produce the effector proteins undergo DNA multiplication and their nuclei become grossly enlarged. Similarly, the soybean root cells that form the syncytium feeding site multiply their DNA content and their nuclei similarly become enlarged.
Interestingly, we do not know why, and to which extend this is happening! Available literature from other systems suggests that DNA duplication does not necessarily serve to alter gene dosage but raises the specter that there also are structural changes to certain gene regions. In other words, we do not know how many genome copies are ultimately produced, whether whole genomes are replicated or just certain regions, if duplication is of high fidelity or if rearrangements take place, and ultimately, we do not know what influence all this has on the resultant gene expression in the nematode effector system and in the soybean redifferentiation of syncytial cells. An additional level of intrigue and complexity arises from the question of whether all syncytial soybean cells undergo the same changes or if there are specific changes in certain cell groups. Similarly in the nematode, it would be interesting to know if all cells of a certain gland type are undergoing identical changes or could there be environmental influences and hitherto unknown regulatory mechanisms at work. The exciting news is that all these questions now are decidedly answerable in our laboratory using technology and know-how we have established or easily can establish.
Our enabling preliminary discoveries are that we have established a soybean hairy root composite plant system and an extensive vector repertoire, with which we will be able to swiftly express gene constructs in transgenic soybean roots. Second, we have been using cell-sorting technology to sort plant and nematode nuclei by size and appearance and will be able to perform transcriptomic and genomic analyses of sorted nuclei.
(2.5-year project funded fall 2024)