Document Type



Doctor of Philosophy


Biology, Molecular and Cellular Biology

Date of Defense


Graduate Advisor

Xuemin Wang


Xuemin Wang

Teresa Thiel

Bethany Zolman

Lon Chubiz


Phospholipase D (PLD) hydrolyzes phospholipids to produce phosphatidic acid (PA) and plays important roles in plant growth, development, and stress response. Of 12 PLDs in Arabidopsis, PLDε is involved in nitrogen response in Arabidopsis and canola, but the mechanism remained elusive. This study was undertaken to investigate how PLDε mediates plant response to nitrogen availability. Nitrogen deficiency induces an increase in PLDε transcript and protein levels and an increased association with intracellular membranes. PLDε interacts with autophagy-related protein 8e (ATG8e), and two of the four predicted ATG8-interacting motifs in PLDε are required for PLDε-ATG8e interactions. PLDε hydrolyzes phosphatidylethanolamine (PE) conjugated to ATG8 and the lipidation and delipidation of ATG8 are essential for the formation of autophagosomes. PLDε-knockout plants display fewer autophagosomes and decreased degradation of autophagy substrate proteins compared with wildtype Arabidopsis under nitrogen deficiency. In addition, this study shows that overexpression of PLDε enhances soybean growth under nitrogen deficiency and increases seed production but affects adversely seed viability during storage. To facilitate the study of PA’s function, Förster resonance energy transfer (FRET)-based PA biosensors have been constructed. The PA biosensors are tethered to the nuclear membrane (NM) to detect PA changes in nuclei as affected by salt and heat treatments. These findings indicate that PLDε promotes autophagy and nitrogen recycling to promote plant growth under nitrogen deficiency. In addition, the PA biosensors will be powerful tools to further study PLD and PA functions with potential application to improving crop production.

Available for download on Friday, May 02, 2025

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