Blu-ray Kelp Gametophyte Development And Its Mechanism

The growth and development of Laminaria gametophyte were greatly influenced by light. Using monochromatic blue light (470 nm) and red light (660 nm) as light sources, we analyzed the light effects on development of Laminaria japonica Aresch. gametophytes. The gametophytes were obtained from zoosopores collected in Sept. 2003, Apr. 2004, May 2004 and July 2004 respectively. It was found that the germination of embryospore did not depend on wavelength and light irradiance, while the growth rate of the gametophytes were stimulated by increasing irradiance of both blue light (BL) and red light (RL), furthermore, the effect of BL was more obvious than that of RL. Under BL (73.90 μmol photons · m-2 · s-1) irradiance, unicellular female gametophytes and multicellular male gametophytes, developed from zoospores released from Laminaria sorus in Apr., produced eggs and sperms, and fertilized to develop into juvenile sporophytes; in contrast, the gametophytes from zoospores collected in May, July or Sept. became multicellular but did not form oogonia and antheridia. Under BL (24.47 μmol photons · m-2 · s-1), RL (25.60 μmol photons · m-2 · s-1) and WL (24.24 μmol photons · m-2 · s-1) irradiance, all gametophytes continued to growth indefinitely. Under lower light irradiance (2.18 μmol photons · m-2 · s-1 of BL or 3.77 μmol photons · m-2 · s-1 of RL), the growth and development of gametophytes were hinded after the germination of embryospores. We believed that times of Laminaria sporangium maturation could affect the responsing behavior of gametophytes to blue light. In addition, the fertilization of gametophytes also depended on blue light, and only sufficient BL irradiance could yield this reproductive effect. It was presumed that possible existence of cryptochrome- or phototropin-like BL photoreceptors involved in BL effect on the early development of Laminaria gametophytes. To verify the mechanism of the BL effect, and target the genes involved in the blue-light induction to the development of L. japonica gametophytes, PCR amplification was conducted with valid extracted genomic DNA and cDNA respectively. A pair of degenerate primers was designed, referred to the cDNA and protein sequences of cryptochrome from Arabidopsis thaliana, Adiantum capillus-veneris and Chlamydomonas reinhardtii. With PCR amplification, two bands of about 1000 bp and 500 bp were obtained, only the 1000 bp DNA was cloned successfully. Sequence analysis indicated that it was not consistent with the desire sequence. Furthermore, with primers specific to the chromophore binding region of cryptochrome, unique band of about 400 bp was amplified using RT-PCR method, it was pity that the ligation was not successful, detail study is needed in the future.