Cloning, expression, and characterization of carbonic anhydrase genes from Pyropia haitanensis (Bangiales, Rhodophyta)

Carbonic anhydrases (CAs) play important roles in the utilization of inorganic carbon and have been studied in many higher plants and algae. Herein, based on unigene sequences from Pyropia haitanensis, six full-length CA of P. haitanensis (PhCA) genes were obtained by rapid amplification of complementary DNA (cDNA) ends, or by direct polymerase chain reaction (PCR), and named Ph alpha CA1, Ph alpha CA2, Ph beta CA1, Ph beta CA2, Ph beta CA3, and Ph gamma CA1. The full-length cDNAs of the six PhCA genes comprised 1156, 1151, 1146, 847, 1124, and 1013 nucleotides, respectively. The encoded proteins were 275, 287, 206, 245, 307, and 290 amino acids, with isoelectric points of 10.26, 5.40, 6.03, 6.42, 7.66, and 4.75, respectively. On the basis of conserved motifs and phylogenetic tree analysis, the PhCAs were divided into three CA classes: Ph alpha CA1 and Ph alpha CA2 are alpha-CAs; Ph beta CA1, Ph beta CA2, and Ph beta CA3 are beta-CAs; and Ph gamma CA1 is a gamma-CA. In different CO2 concentrations, the expression levels of Ph beta CA2, Ph beta CA3, and Ph gamma CA1 showed no significant changes; however, the expression levels of Ph alpha CA1, Ph alpha CA2, and Ph beta CA1 decreased significantly under high CO2. The expression level of each Ph beta CA gene was significantly higher in the sporophytes than in the gametophytes; however, the expression levels of Ph alpha CA and Ph gamma CA in the sporophytes were significantly lower than those in the gametophytes. The expression level of each PhCA under desiccation and high-temperature stress had a different pattern. These results suggested that PhCAs play important roles in the utilization of inorganic carbon of P. haitanensis. Additionally, the expressions of PhCAs were significantly affected by environmental stresses.