JOURNAL ARTICLE

Localization of putative carbonic anhydrases in two marine diatoms, Phaeodactylum tricornutum and Thalassiosira pseudonana

Masaaki Tachibana, Andrew E Allen, Sae Kikutani, Yuri Endo, Chris Bowler, Yusuke Matsuda
Photosynthesis Research 2011, 109 (1-3): 205-21
21365259
It is believed that intracellular carbonic anhydrases (CAs) are essential components of carbon concentrating mechanisms in microalgae. In this study, putative CA-encoding genes were identified in the genome sequences of the marine diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana. Subsequently, the subcellular localizations of the encoded proteins were determined. Nine and thirteen CA sequences were found in the genomes of P. tricornutum and T. pseudonana, respectively. Two of the β-CA genes in P. tricornutum corresponded to ptca1 and ptca2 identified previously. Immunostaining transmission electron microscopy of a PtCA1:YFP fusion expressed in the cells of P. tricornutum clearly showed the localization of PtCA1 within the central part of the pyrenoid structure in the chloroplast. Besides these two β-CA genes, P. tricornutum likely contains five α- and two γ-CA genes, whereas T. pseudonana has three α-, five γ-, four δ-, and one ζ-CA genes. Semi-quantitative reverse transcription PCR performed on mRNA from the two diatoms grown in changing light and CO(2) conditions revealed that levels of six putative α- and γ-CA mRNAs in P. tricornutum did not change between cells grown in air-level CO(2) and 5% CO(2). However, mRNA levels of one putative α-CA gene, CA-VII in P. tricornutum, were reduced in the dark compared to that in the light. In T. pseudonana, mRNA accumulation levels of putative α-CA (CA-1), ζ-CA (CA-3) and δ-CA (CA-7) were analyzed and all levels found to be significantly reduced when cells were grown in 0.16% CO(2). Intercellular localizations of eight putative CAs were analyzed by expressing GFP fusion in P. tricornutum and T. pseudonana. In P. tricornutum, CA-I and II localized in the periplastidial compartment, CA-III, VI, VII were found in the chloroplast endoplasmic reticulum, and CA-VIII was localized in the mitochondria. On the other hand, T. pseudonana CA-1 localized in the stroma and CA-3 was found in the periplasm. These results suggest that CAs are constitutively present in the four chloroplastic membrane systems in P. tricornutum and that CO(2) responsive CAs occur in the pyrenoid of P. tricornutum, and in the stroma and periplasm of T. pseudonana.

Full Text Links

Find Full Text Links for this Article

Discussion

You are not logged in. Sign Up or Log In to join the discussion.

Related Papers

Remove bar
Read by QxMD icon Read
21365259
×

Save your favorite articles in one place with a free QxMD account.

×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"