Plant polyamine alternative pathways

Project Summary

Polyamines are multifunctional biological molecules found in all living organisms. In plants, polyamines respond to biotic and abiotic stressors, so understanding their regulatory and biosynthetic pathways provide insight to the plant defense system. An Arabidopsis thaliana acetyltransferase, NATA1, has been shown to have important regulatory functions on plant polyamines. The goal of this project was to further explicate the function of NATA1 and two decarboxylases, ADC1 and ADC2, in a potential polyamine/acetylpolyamine biosynthetic pathway and their part in plant biotic stress response.

Genotyped nata1 mutant Arabidopsis leaf samples were analyzed on LC-MS after 3 days of Nδ-acetylornithine treatment. The detection of acetylputrescine suggests the existence of a yet-unidentified alternative pathway to polyamine formation. Given the somewhat similar structure of arginine and Nδ-acetylornithine, we tested whether ADC1 and ADC2 also function as Nδ-acetylornithine-decarboxylase. Arabidopsis ADC1 and ADC2 were cloned under cauliflower mosaic virus (CaMV) 35S promoter and overexpressed in Nicotiana benthamiana before being purified. Acetylputrescine accumulation was detected when purified ADC1 and ADC2 were co-incubated withNδ-acetylornithine in an in vitro assay.  To investigate the biological function of the alternative pathway, Pseudomonas syringae was infiltrated into Col-0, nata1, adc1, adc2, nata1 adc1 and nata1 adc2 mutant Arabidopsis plants. Polyamine level was analyzed using HPLC and transcript level of defense-related marker genes and genes on polyamine biosynthesis pathway (AIH, CPA, ADC1, ADC2, and NATA1) were quantified using qPCR. My results suggest the existence of an alternative polyamine biosynthesis pathway and further investigation is warranted to assess how these acetylated polyamines function in the plant defense system.

My Experience

My summer as a PGRP intern has been both challenging and extremely rewarding. I came into this program knowing little to nothing about molecular biology and genetics. Thankfully my mentor, Yann-Ru Lou, was an amazing teacher and role model. She has taught me many lab skills that will be useful well into graduate school. She has also taught me the essential skill of how to be patient and perseverant when experiments or machines do not work. In the future I hope I am lucky enough to be a part of a lab as brilliant and helpful as the Jander Lab. I am truly thankful for my summer at BTI and all the people that have contributed to my growth as an aspiring plant scientist. I have never been more excited to attend graduate school and continue conducting plant science research.