title: Growth and cell cycle of Ulva compressa (Ulvophyceae) under LED illumination.
abstract: The cell-cycle progression of Ulva compressa is diurnally gated at the G1 phase in accordance with light-dark cycles. The present study was designed to examine the spectral sensitivity of the G1 gating system. When blue, red, and green light-emitting diodes (LEDs) were used for illumination either alone or in combination, the cells divided under all illumination conditions, suggesting that all colors of light were able to open the G1 gate. Although blue light was most effective to open the G1 gate, red light alone or green light alone was also able to open the G1 gate even at irradiance levels lower than the light compensation point of each color. Occurrence of a period of no cell division in the course of a day suggested that the G1 gating system normally functioned as under ordinary illumination by cool-white fluorescent lamps. The rise of the proportion of blue light to green light resulted in increased growth rate. On the other hand, the growth rates did not vary regardless of the proportion of blue light to red light. These results indicate that the difference in growth rate due to light color resulted from the difference in photosynthetic efficiency of the colors of light. However, the growth rates significantly decreased under conditions without blue light. This result suggests that blue light mediates cell elongation and because the spectral sensitivity of the cell elongation regulating system was different from that of the G1 gating system, distinct photoreceptors are likely to mediate the two systems.
authors.affiliation: Graduate School of Science and Technology, Nagasaki University, Bunkyo-machi, Nagasaki, 852-8521, Japan.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Kuwano
authors.affiliation: Graduate School of Science and Technology, Nagasaki University, Bunkyo-machi, Nagasaki, 852-8521, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Abe
authors.affiliation: Faculty of Fisheries, Nagasaki University, Bunkyo-machi, Nagasaki, 852-8521, Japan.
authors.forename: Yukari
authors.initials: Y
authors.lastname: Nishi
authors.affiliation: Faculty of Fisheries, Nagasaki University, Bunkyo-machi, Nagasaki, 852-8521, Japan.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Seno
authors.affiliation: Institute for East China Sea Research, Nagasaki University, Taira-machi, Nagasaki, 851-2213, Japan.
authors.forename: Gregory N
authors.initials: GN
authors.lastname: Nishihara
authors.affiliation: Faculty of Environmental Studies, Nagasaki University, Bunkyo-machi, Nagasaki, 852-8521, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Iima
authors.affiliation: Laboratory of Cell Cycles of Algae, Institute of Microbiology, Academy of Sciences of the Czech Republic (ASCR), Opatovický mlýn, 37981, Třeboň, Czech Republic.
authors.forename: Vilém
authors.initials: V
authors.lastname: Zachleder
keywords: G1 gate; Ulva; cell cycle; cell division; cell elongation; diurnal rhythm