Utilizing the Effective Xanthophyll Cycle for Blooming of Ochromonas smithii and O. itoi (Chrysophyceae) on the Snow Surface

Snow algae inhabit unique environments such as alpine and high latitudes, and can grow and bloom with visualizing on snow or glacier during spring-summer. The chrysophytes Ochromonas smithii and Ochromonas itoi are dominant in yellow-colored snow patches in mountainous heavy snow areas from late May to early June. It is considered to be effective utilizing the xanthophyll cycle and holding sunscreen pigments as protective system for snow algae blooming in the vulnerable environment such as low temperature and nutrients, and strong light, however the study on the photoprotection of chrysophytes snow algae has not been shown. To dissolve how the chrysophytes snow algae can grow and bloom under such an extreme environment, we studied with the object of light which is one point of significance to this problem. We collected the yellow snows and measured photosynthetically active radiation at Mt. Gassan in May 2008 when the bloom occurred, then tried to establish unialgal cultures of O. smithii and O. itoi, and examined their photosynthetic properties by a PAM chlorophyll fluorometer and analyzed the pigment compositions before and after illumination with high-light intensities to investigate the working xanthophyll cycle. This experimental study using unialgal cultures revealed that both O. smithii and O. itoi utilize only the efficient violaxanthin cycle for photoprotection as a dissipation system of surplus energy under prolonged high-light stress, although they possess chlorophyll c with diadinoxanthin

Morphological and genetic variation in the cosmopolitan snow alga Chloromonas nivalis (Volvocales, Chlorophyta) from Japanese Mountainous Area

http://dx.doi.org/10.1508/cytologia.73.91全文の閲覧は上記URLをご覧ください。元論文掲載誌書誌事項:Cytologia. 73(1):96-96(2008

Microscopy photographs of A, <i>Ochromonas itoi</i>; B, <i>Ochromonas smithii</i>; C, landscape of yellow snow caused by <i>Ochromonas itoi</i> and <i>Ochromonas smithii</i> on/in the deposited snow surface in Mt. Gassan.

<p>Microscopy photographs of A, <i>Ochromonas itoi</i>; B, <i>Ochromonas smithii</i>; C, landscape of yellow snow caused by <i>Ochromonas itoi</i> and <i>Ochromonas smithii</i> on/in the deposited snow surface in Mt. Gassan.</p

Time course of xanthophyll cycle pigment changes in a cell suspension of <i>Ochromonas itoi</i> in low-light (LL) during 1-h illumination after 6-h high-light (HL) illumination.

<p>Pigments are normalized to chlorophyll <i>a</i> (Chl.<i>a</i>). Values are means of three independent records, and error bars are standard deviations. A, Epoxidation of zeaxanthin (Zx) from antheraxanthin (Ax) to Vx; B, epoxidation of diatoxanthin (Dtx) to diadinoxanthin (Ddx).</p

Changes in xanthophyll cycle pigments in <i>Ochromonas itoi</i> and <i>Ochromonas smithii</i> after 6-h high-light (HL) incubation.

<p>Changes in xanthophyll cycle pigments in <i>Ochromonas itoi</i> and <i>Ochromonas smithii</i> after 6-h high-light (HL) incubation.</p

Molecular structures of the xanthophyll cycle pigments mentioned in the text.

<p>Arrows between pigments denote enzymatic conversions caused by xanthophyll cycling.</p

Pigment composition of <i>Ochromonas itoi</i> and <i>Ochromonas smithii</i> before high light (HL) and after 6-h HL incubation.

<p>Chl.<i>a</i>, chlorophyll <i>a</i>; Chl.<i>c</i>, chlorophyll <i>c</i>; Fx, fucoxanthin; Ddx, diadinoxanthin; Dtx, diatoxanthin; Vx, violaxanthin; Ax, antheraxanthin; Zx, zeaxanthin; α-Car, α-carotene; β-Car, β-carotene. Values are means of three independent measurements, and s.d. are standard deviation.</p><p>*¹ Chl.<i>c</i>, Chl.<i>c</i>1+<i>c</i>2</p><p>*² α-Car and β-Car were not absolutely separated using this study's HPLC method. α-Car was only detected in <i>O. itoi</i>.</p

Time course of xanthophyll cycle pigment changes in <i>Ochromonas itoi</i> in high-light (HL) after 6-h HL illumination, followed by 1-h low-light (LL) illumination.

<p>Pigments are normalized to chlorophyll <i>a</i> (Chl.<i>a</i>). Values are means of three independent records, and error bars are standard deviations. A, Deepoxidation of violaxanthin (Vx) from antheraxanthin (Ax) to zeaxanthin (Zx); B, deepoxidation of diadinoxanthin (Ddx) to diatoxanthin (Dtx).</p