Joseph C. Polacco

Professor Emeritus of Biochemistry

Email:	polaccoj@missouri.edu
Phone:	(573) 882-4845
Fax:	(573) 882-5635
Mailing Address:	Biochemistry 117 Schweitzer Hall University of Missouri-Columbia Columbia, MO 65211
Research Areas:	Nitrogen and nitric oxide metabolism in plants.

Educational Background

Notable Honors and Service

Research Description

Joe Polacco's group takes a molecular genetics and functional genomics approach to examine nitric oxide (NO) production and action in plants. NO has been shown to be involved in responses to abiotic and biotic challenges and in hormonal signaling of formation of lateral roots, adventitious roots and root hairs). One potential source of NO is arginine, via the action of an NO synthase (NOS) which has been shown to be the only source in animals. The identity of a plant NOS is currently controversial; however, there are indications that increased arginine leads to enhanced NO production in several systems. The Polacco lab has shown a possible relationship between NO production and arginase, an enzyme that converts arginine to urea and ornithine. Mutants lacking either of the Arabidopsis arginases appear to produce more NO and have enhanced responses to exogenous NO or auxin.

Plant arginases are mitochondrial, and a related emphasis is to examine roles of mitochondrial arginine transporters in controlling access of arginine to arginase and to a possible mitochondrial NOS. Two inner membrane mitochondrial carrier proteins have been identified. They are functional in yeast and mediate the exchange of basic amino acids when incorporated into artificial liposomes,. One of the carriers, BAC2, recognizes both arginine and the NOS product citrulline. Mutants deficient in BAC1 or BAC2 and an over-expressing line of BAC2 are being examined now for NO responses.

A long-standing interest of the Polacco lab has been on the assimilatory roles, and Ni activation, of the soybean ureases. This interest is now being refocused on insecticidal and fungitoxic properties of the urease isozymes, in collaboration with the labs of Celia Carlini and Giancarlo Pasquali (Universidade do Rio Grande do Sul, Brazil). Joe Polacco is relocating to the Carlini lab; however, he maintains an association with MU, and is involved in training of personnel from both institutions.

Selected Publications

Todd, CD, Tipton P, Blevins DG, Pineda M, Piedras P, Polacco JC (2006) Update on ureide degradation in legumes. J Exp Botany 57: 5-12

Lombardo MC, Graziano M, Polacco JC, Lamattina L (2006) Nitric oxide functions as a positive regulator of root hair development. Plant Signaling & Behavior 1: 28-33

Todd CD, Polacco JC (2006) AtAAH, an allantoate amidohydrolase from Arabidopsis thaliana. Planta 223: 1108 - 1113

Todd, CD, Tipton PA, Blevins DG, Pineda M, Piedras P, Polacco JC (2006) Update on ureide degradation in legumes. J Exp Botany 57: 5-12

Lombardo MC, Graziano M, Polacco JC, Lamattina L (2006) Nitric oxide functions as a positive regulator of root hair development. Plant Signaling & Behavior 1: 28-33

Palmieri L, Todd CD, Arrigoni R, Hoyos ME, Santoro A, Polacco JC (2006) Arabidopsis mitochondria have two basic amino acid transporters with partially overlapping specificities and differential expression in seedling development. Biochimica et Biophysica Acta 1757: 177-1283