Graduate student The university of Texas in Austin Austin, Texas
Body of Abstract: Apyrases are nucleoside triphosphate diphosphohydrolases (NTPDases) that can limit the concentration of NTPs and NDPs, but not NMPs. They play key roles in controlling plant growth and development. A pea apyrase, called psNTP9 (abbreviated as PS), was originally isolated from nuclei of etiolated pea plumules. Previous work showed that PS complemented the yeast phosphate (Pi)-transport mutant pho84. Ectopically expressing PS in Arabidopsis and soybeans increased their growth. Two site-directed mutations generated an altered domain in PS, and this modified version, called DM, was able to promote Pi uptake better than PS and promote more seed production in transgenic Arabidopsis and soybean. Western blot results showed that in transgenic yeast, both PS and DM are expressed in the nuclei of these fungi. Both are also associated with chromatin proteins in yeast nuclei, but, as judged by proteomic and mass spectrometry analyses, PS and DM co-purify with different chromatin-associated proteins. Similarly, when expressed in Arabidopsis or soybeans, PS and DM co-purify with nuclei, and, in transgenic Arabidopsis, PS requires its nuclear localization signal to co-purify with nuclei. RNA-seq analysis showed the gene expression changes induced by PS differ from those induced by DM in Arabidopsis and yeast. The above results indicate that the PS and DM apyrases can function in the nuclei of yeast, Arabidopsis and soybeans, and their expression in these organisms can promote Pi uptake and growth in part by altering the expression level of regulatory genes.