Graduate Research Assistant Purdue University Lafayette, Indiana
Body of Abstract: The study of vascular tissue is of interest to researchers due to its role in transporting signaling molecules and nutrients. Our laboratory is developing species in the genus Plantago as models for vascular biology studies, due to their unique attribute of having easily extractable vascular tissue. In-depth studies on relationships between gene function and their associated phenotype on previously identified genes expressed in Plantago vascular tissue are limited due to the lack of a genetic manipulation toolkit for the species. We developed a transformation method for one species of Plantago, narrowleaf plantain (P. lanceolata), using Agrobacterium tumefaciens mediated transformation to achieve a transformation efficiency of ~20%. To verify the usefulness of our method, we studied the carbohydrate phloem loading mechanisms in narrowleaf plantain. Different from most plants, which typically transport one type of carbohydrate in their phloem, Plantago species transport two; sucrose and sorbitol. However, the phloem-loading mechanisms for these carbohydrates have not been experimentally studied. We have generated transgenic narrowleaf plantains in which the phloem-expressed sucrose transporter gene was knocked out via CRISPR/Cas9. The retarded growth of the transgenic plant suggests that sucrose is loaded to the phloem via an apoplastic pathway. We are also developing similar CRISPR/Cas9 knockouts for the sorbitol transporter. Once the plants are produced, we will do a series of experimental comparisons between the two types of knockout plants. This study will dissect the phloem loading pathway for sucrose and sorbitol and reveal the importance of phloem mobile carbohydrates to the growth of the plant.