中国水产科学2017，Vol.24Issue(6)：1342-1353,12.DOI:10.3724/SP.J.1118.2017.16324
盐胁迫对雨生红球藻虾青素累积、虾青素合成相关酶基因表达和抗氧化指标的影响
Effects of salt stress on astaxanthin accumulation, gene expression of astaxanthin synthesis-related enzymes, and antioxidant indices in Hae-matococcus pluvialis
摘要
Abstract
Haematococcus pluvialis (Chlorophyceae, Order Volvocales), a freshwater green microalgal species, has commercial value owing to its ability to accumulate high concentrations of astaxanthin (up to 5% of dry weight). Astaxanthin (3,3′-dihydroxy-β, β-carotene-4,4′-dione) is a red ketocarotenoid which has many important biologi-cal functions, including antioxidant activity, regulation of immune responses, and disease resistance, and has the potential for application in the aquacultural, nutraceutical, pharmaceutical, and cosmetic industries. H. pluvialis has a distinctive lifecycle as it exhibits a green motile stage and a red non-motile resting stage called an aplano-spore. In general, astaxanthin accumulation in H. pluvialis is restricted to the aplanospore stage. Astaxanthin is accumulated in extra-plastidic lipid vesicles as a secondary carotenoid, and it is believed to be synthesized in re-sponse to oxidative stress in the red aplanospore stage under unfavorable environmental conditions such as high light, temperature, and salinity, or low nutrient availability. Several enzymes such as lycopene β-cyclase (Lcy),β-carotenoid hydroxylase (CrtR-B) and β-carotene ketolase (Bkt) are involved in the astaxanthin biosynthesis pathway in H. pluvialis. Lcy catalyzes the formation of β-carotene from lycopene, and CrtR-B and Bkt catalyze further steps leading to astaxanthin synthesis. Changes in expression of the genes encoding these three enzymes can criti-cally affect the biosynthesis and accumulation of astaxanthin in H. pluvialis. In addition, various antioxidant en-zymes including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) also have important protective effects for combating oxidative stress under unfavourable environmental conditions. We aimed to explore the effect of salt stress on astaxanthin accumulation in H. pluvialis, by examining the mechanism of astaxanthin synthesis and the relationship between the different antioxidant mechanisms in H. pluv-ialis at high salinity. We examined its growth rate; astaxanthin content; Lcy, CrtR-B, and Bkt gene expression lev-els; SOD, CAT, and GSH-Px activities; and malondialdehyde (MDA) content at four salinity levels (0.04 mol/L, 0.08 mol/L, 0.12 mol/L, and 0.16 mol/L) over three timescales (3 days, 6 days, and 9 days). Our results showed that the density of H. pluvialis decreased under increasing salinity over different periods of time, while its mortality rate and aplanospore proportion increased with increasing salt stress concentration by the ninth day of stress. Asta-xanthin content, Lcy, CrtR-B, and Bkt gene expressions increased over time with increasing salinity. SOD, CAT, and GSH-Px activities and MDA content also increased in comparison to H. pluvialis grown at the control level of 0 mol/L NaCl, and significantly increased at the 0.12 mol/L NaCl level (P<0.05). Astaxanthin content and Lcy, CrtR-B, and Bkt gene expressions were lower during the early and mid-stages of salt stress (e.g., on the third and sixth days of observation), and increased by the ninth day. Meanwhile, SOD, CAT, and GSH-Px activities and MDA content were higher during early and mid-stage stress, but were lower by the ninth day. These results suggest that salt stress can improve astaxanthin accumulation over time in H. pluvialis at the appropriate level of salt stress, despite its negative effects on growth. Astaxanthin synthesis in H. pluvialis is promoted mainly through an increase in the transcription level of astaxanthin synthesis-related enzyme genes under salt stress, and the antioxidant activities of astaxanthin and antioxidant enzymes complement one other to protect from oxidative damage under salt stress. This study provides a new insight into the astaxanthin synthesis and antioxidant mechanisms in H. pluvialis.关键词
雨生红球藻/盐胁迫/虾青素/Lcy/CrtR-B/Bkt/抗氧化酶/MDAKey words
Haematococcus pluvialis/salt stress/astaxanthin/Lcy/CrtR-B/Bkt/antioxidant enzyme/MDA分类
农业科技引用本文复制引用
江红霞,林雄平,轩文娟..盐胁迫对雨生红球藻虾青素累积、虾青素合成相关酶基因表达和抗氧化指标的影响[J].中国水产科学,2017,24(6):1342-1353,12.基金项目
河南省重点科技攻关项目(102102210181) （102102210181）
河南省水产学重点学科基金项目(2012). （2012）
