Elucidating the function of inositol pyrophosphate signaling pathways in Arabidopsis thaliana

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Virginia Tech


Phosphate (Pi) is an essential nutrient for plants, required for plant growth and seed viability. When Pi is limited, plants undergo dynamic morphological and metabolic changes to leverage available Pi, known as the Phosphate Starvation Response (PSR). The inositol phosphate (InsP) signaling pathway is a crucial element of the plant's ability to regulate the PSR and respond to changing energy conditions. InsPs are synthesized from the cyclic 6-carbon polyol scaffold, myo-inositol. Inositol hexakisphosphate (InsP6) is the most abundant InsP signaling molecule and can be phosphorylated by the multifunctional inositol tetrakisphosphate 1-kinase 1 (ITPK1) and diphosphoinositol pentakisphosphate (VIP) kinases, resulting in inositol pyrophosphates (PP-InsPs). PP-InsPs have high energy bonds and have been linked to Pi maintenance and energy homeostasis in yeast, plants, and mammals. However, the precise mechanism(s) by which PP-InsPs act within plant signaling pathways remains to be determined. Two approaches to understand the role of PP-InsPs in plants are described within this dissertation. The first approach analyzes genetic loss-of-function vip1/vip2 double mutants, and their responses to low Pi conditions. Specifically, vip1/vip2 double mutant gene expression and lipid remodeling patterns in response to low Pi were characterized. We found that vip1-2/vip2-2 had an impacted lipid remodeling response under low Pi conditions, whereas ipk1 had altered lipid composition under Pi-replete conditions. In a complementary approach, a gain-of-function in either the ITPK1 or the kinase domain of VIP (VIP2KD) were constructed in transgenic Arabidopsis thaliana plants. Both ITPK1 and VIP2KD transgenic plants contain elevated levels of the specific inositol pyrophosphate, InsP8. Elevated InsP8 in both types of plants results in changes in growth and senescence phenotypes, delayed time to flowering, Pi accumulation, and altered PSR gene expression. The data from both approaches suggest new roles for PP-InsPs in the regulation of the PSR and other signaling pathways in plants. To enhance my teaching and leadership skills, I participated in the Graduate Teaching Scholars (GTS) program. As a GTS, I worked with the Virginia Tech Research and Extension Experiential Learning (VT-REEL) program where I developed a structured mentorship program for undergraduate and graduate students and created a professional development workshop series. During the COVID-19 pandemic, I developed an online version of the VT-REEL program. Using inclusive pedagogy practices and surveys from the participants, we compiled the best practices for moving a summer undergraduate research program online. These practices come from surveyed participants in the 2020 and provides strategies that can be tailored to various online research experiences and be implemented in both online and in-person formats.



Inositol Phosphate, Inositol Pyrophosphate, Inositol, Phosphorous, Phosphate, Phosphate Sensing, VIP, ITPK1, Phosphate Starvation Response