TITLE:
Phototropism in the Marine Red Macroalga Pyropia yezoensis
AUTHORS:
Megumu Takahashi, Koji Mikami
KEYWORDS:
Phototropism, Gametophyte, Sporophyte, Conchosporangia, Pyropia yezoensis
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.7 No.17,
December
8,
2016
ABSTRACT: Phototropism is a response to the direction of light that guides growth orientation
and determines the shape of plants to optimize photosynthetic activity. The phototropic
response is present not only in terrestrial plants but also in water-living algae.
However, knowledge about phototropism in Bangiophycean seaweeds is limited.
Here, we examined the phototropic response of the red alga Pyropia yezoensis to
elucidate the regulatory mechanism of phototropism in Bangiophyceae. When leafy
gametophytes and filamentous sporophytes of P. yezoensis were cultured under directional
light, phototropism was observed in the gametophytes. Conchosporangia
on the sporophytes also exhibited phototropism. Phototropism was positive in the
majority of gametophytes and conchosporangia but in some cases was negative. In
addition, a strong phototropic response occurred under white light, whereas blue and
red light elicited minor and no responses, respectively. This observation is in contrast
with the phototropic response in terrestrial plants and several algae, in which blue
light is responsible for positive phototropism. Surprisingly, the genome of P. yezoensis has no homologues of the photoreceptors for blue and red light, revealing differences
in the regulation of phototropism between terrestrial plants and P. yezoensis .
Studies on the phototropism in P. yezoensis could shed light on the evolutional divergence
of phototropic responses in plants.