Differential Expression of Carotenogenic Genes, Associated Changes on Astaxanthin Production and Photosynthesis Features Induced by JA in H. pluvialis

Zhengquan Gao,Hongxin Lv,Yuefeng Zhao,Naihao Ye,Yitao Wang,Dong Xu,Chunxiao Meng,Xiaowen Zhang,Lingling Chen,Liming Yang Liming Yang

doi:10.1371/journal.pone.0042243

Abstract

Haematococcus pluvialis is an organism that under certain conditions can produce astaxanthin, an economically important carotenoid. In this study, the transcriptional expression patterns of eight carotenogenic genes of H. pluvialis in response to jasmonic acid (JA) were evaluated using real-time PCR. Astaxanthin accumulation action and photosynthesis flourescence were monitored at the same time. The results showed all eight genes exhibited higher transcriptional expression significantly under JA treatments. JA25 (25 mg/L) induction had greater effect (>10-fold up-regulation) on the transcriptional expression of pds, crtR-B and lyc than on ipi-1, ipi-2, psy, bkt2, and crtO. JA50 (50 mg/L) treatment had greater impact on the transcriptional expression of ipi-1, ipi-2, psy, crtR-B and crtO than on pds, lyc and bkt2. Astaxanthin biosynthesis in the presence of JA appeared to be up-regulated mainly by psy, pds, crtR-B, lyc, bkt2 and crtO at the transcriptional level and ipi-1, ipi-2 at both transcriptional and post-transcriptional levels. Under JA induction, the photosynthetic efficiency [Y (II)] and the maximum quantum efficiency of PS II (Fv/Fm) decreased significantly, but the non-photochemical quenching of chlorophyll fluorescence (NPQ) increased drastically with the accumulation of astaxanthin.

Highlights

Astaxanthin (3,39-dihydroxy-b,b-carotene-4,4-dione) is a red ketocarotenoid used as a pigmentation source in aquaculture and the nutraceutical, pharmaceutical, and cosmetic industries [1]
jasmonic acid (JA) promoted nicotine biosynthesis in transgenic tobacco by causing over-expression of allene oxide cyclase from Hyoscyamus niger [20]. These results suggest that JAs could be used as an effective regulator to stimulate astaxanthin production in H. pluvialis
In order to better understand the regulatory underpinnings of JA induced H. pluvialis accumulating astaxanthin, the growth curves of alga cells, astxanthin concentration, photosynthesis flourescence and the transcriptional expression patterns of eight carotenogenic genes were studied in our experiment

Summary

Introduction

Astaxanthin (3,39-dihydroxy-b,b-carotene-4,4-dione) is a red ketocarotenoid used as a pigmentation source in aquaculture and the nutraceutical, pharmaceutical, and cosmetic industries [1]. The freshwater unicellular alga Haematococcus pluvialis is a good astaxanthin-producing organism since it can accumulate astaxanthin up to 4% of dry weight [2]. H. pluvialis synthesises abundant astaxanthin in response to various stress conditions, such as high light, salinity, acetate addition [3], nutrient stress [4], and high carbon/nitrogen ratio [5]. The following carotenoid biosynthesis genes have been cloned and characterized in H. pluvialis: they are isopentenyl diphosphate isomerase gene (ipi) [7], phytoene synthase gene (psy) [8], phytoene desaturase gene (pds) [6,9], lycopene b cyclase gene (lyc) [8], b-carotenoid oxygenase gene (crtO) [10], three carotenoid ketolase genes (bkts) [10], and carotenoid hydroxylase gene (crtR-B) [11]. Considerable efforts have been focused on understanding regulation of carotenogenic genes related to astaxanthin biosynthesis in H. pluvialis and on the physiological role of astaxanthin in the response to various stresses

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