postdoctoral researcher Purdue University West Lafayette, Indiana
Body of Abstract: Most prior studies related to mineral deficiency focused on local signaling in the root. However, various evidence showed systemic signaling mediated by vascular tissues (i.e., xylem and phloem) also plays indispensable roles in adapting plants to low minerals. Although collecting pure xylem sap is easy, harvesting authentic phloem tissue/sap is challenging. Our work and those of others showed that most of currently used phloem tissue/sap collection methods could lead to contamination issues during sampling process.
Plantains, including P. major and P. lanceolate, which have been largely ignored in vascular biology study, possess a few characteristics for being used as model species. Compared to the trivial amount (in the range of microgram or microliter) of vascular tissues collected via most other methods, it takes less than five seconds to collect 200-300 mg of PURE vascular tissues from plantains. Tissue culture transformation method is available for both P. majorand P. lanceolate. Our lab has been using P. major to study vascular tissue-specific responses to low minerals, including nitrogen (N), phosphate (Pi) and iron (Fe). We found that most Pi and Fe deficiency responsive genes are also N deficiency responsive, but vice versa is not true. The results on Pi deficiency study showed that (1) sucrose, auxin, and a few other hormones localized in vascular tissues are involved in responses to low Pi; (2) RNA-Seq analysis showed that hormone transport and biosynthesis, glycolysis, phosphate metabolism and remobilization, sucrose loading and synthesis are involved in phosphate deficiency responses; (3) tissue specific gene expression analysis showed that vascular tissues have more dramatic responses than the surrounding tissues to early phosphate (24 hrs) deficiency. In addition, we over-expressed a Pi deficiency responsive gene from vascular tissues in Arabidopsis, and the transgenic plants showed earlier flowering phenotype compared with control plants.