CHARACTERIZATION OF THE Arabidopsis thaliana PHOSPHOINOSITIDE-SPECIFIC PHOSPHOLIPASE C GENE FAMILY

¹ Department of Agronomy, Iowa State University, Ames, IA 50011

² Department of Genetics, Development and Cell Biology and Department of Statistics, Iowa State University, Ames, IA 50011

Phosphoinositide-specific phospholipases C (PI-PLCs) are key regulators of the second messenger Ca²⁺ in animal cells. Here we report the identification of nine PI-PLC (AtPLC) genes in the genome of Arabidopsis thaliana. AtPLC1, AtPLC4 and AtPLC5 form a gene cluster on chromosome five, AtPLC8 and AtPLC9 are in a tandem array on chromosome three, and AtPLC6 (chromosome two), AtPLC2 and AtPLC7 (chromosome three), and AtPLC3 (chromosome four) occur as singlets. Structurally, these genes are very similar to the mammalian PI-PLC-delta isoform. Expression patterns of all nine genes were studied by RT-PCR and Northern blot analyses as a first step toward understanding the functions of this enzyme. Multiple members of the gene family are differentially expressed in Arabidopsis organs, suggesting putative roles for this enzyme in plant development including tissues and organ differentiation. Five AtPLC genes were induced 1–2 h following infection with an avirulent strain of the bacterial pathogen Pseudomonas syringae pv. tomato, indicating a possible involvement of PI-PLC in the expression of disease resistance. This study also established that steady state transcript levels of most of the AtPLC genes are regulated in response to various environmental stimuli, including cold, salt, nutrient Murashige-Skoog salts, dehydration, and the plant hormone abscisic acid. Increased transcript accumulation of most members of the AtPLC gene family under stress conditions strongly suggests that PI-PLC has a major role in the adaptation of plants to changed environmental conditions.