Ⅲ-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 56 (2023)
RIKEN
Accel. Prog. Rep. 56 (2023)

Growth inhibition of marine red alga Agardhiella subulata throughC-ion beam irradiation
K. Tsuneizumi,∗1 M. Yamada,∗1 M. Mogamiya,∗2 Y. Sato,∗2 and T. Abe∗1
In the Japanese way of life, seaweeds such as laver,kelp, wakame, and hijiki have a long history of use andare consumed in large quantities. Recently, seaweeds
have gained attention as materials for the productionof carrageenan, alginic acid, and agar,1) and their production has been increasing in Asia as an aquaculture marine resource rather than for food. Furthermore, seaweeds contain fucoidan, which has proven tobe eﬀective in hair growth promotion,2) immunostimulatory activities,3) and anti-aging.4) This information
has led to increasing attention to seaweeds as raw materials for functional materials.
Agardhiella subulata, commonly known as edible redalgae, has been discovered as a new material that produces fucoidan,5) and there is much interest in increasing the production of its active ingredients. Breedingnew cultivars with properties such as high yield, highenvironmental adaptability, and high concentrations ofconstituents with human health beneﬁts is desirable
for enhanced value. In this report, to determine theeﬀective conditions of the C-ion beam for red algae
mutagenesis, we calculated the growth in the area of
irradiated regenerating buds.
Small fragments of A. subulata were cultured withNORI SEED (Daiichi Seimo Co., Ltd.), a highly enriched culture solution. A culture medium was prepared using 160 µL of NORI SEED diluted with
300 mL of autoclaved sea water. Small fragments
developed into regenerating buds for three weeks ina stirred 300-mL marine ﬂask containing the culture medium. The ﬂask was placed at 25◦ C for a
12 hours photoperiod with a light intensity of 50 µmol
photons · m−2 s−1 , and the culture medium in the ﬂask
was replaced every week. The regenerating buds werereplaced into 5-mL tubes at each irradiation condition.
Heavy-ion-beam irradiation was performed using C(LET = 30 keV/µm) at 8 irradiation doses of 5, 10,20, 40, 70, 100, 200, and 400 Gy generated at theRIKEN RIBF.6) Four hours after irradiation, eight regenerating buds were inoculated into each 36-mm dishcontaining 3 mL of fresh culture medium for each irradiation condition. The dishes were placed at 25◦ C
for a 12 hours photoperiod with a light intensity of
50 µmol photons · m−2 s−1 , and 150 µL of the 20-foldconcentrated culture medium was added every 2–3 d.
The regenerating buds were photographed every few
days and the sizes of 8 reproducing individuals (n = 8)
were calculated using Image J software version 1.5.17)(Fig. 1).
∗1
∗2

RIKEN Nishina Center
Riken Food Co., Ltd.

- 194 -Fig. 1. Correlation between increasing area of regenerating
buds and C-irradiation dose. A correlation chart using
the average values of increasing area was constructed
for the unirradiated control and irradiated regeneratingbuds. The vertical vars represent the standard errors.

An increase in the area representing the regenerating buds irradiated up to 20 Gy in the correlation chartindicates that they proliferate in the same way as unirradiated controls (Fig. 1). In contrast, the growth inhibition of the regenerating buds is observed in a dosedependent manner eﬀected by 40–400 Gy C-ion beams(Fig. 1). In future studies, we will carry out largescale screening under each irradiation condition, andthe optimum irradiation conditions will be determinedbased on the frequency of the appearances of the mutant lines.
References
1) Y. C. Liao et al., Bioengineered 12, 3787 (2021).
2) I. S. Moon et al., Hear. Res. 282, 236 (2011).
3) R. Li et al., Mar. Drugs 21, 18 (2023).
4) R. Zhang et al., Carbohydr. Polym. 15, 228 (2020).
5) C. Faggio et al., Nat. Prod. Res. 30, 2016 (2015).
6) T. Abe et al., in Plant Mutation Breeding and Biotechnology, edited by Q. Y. Shu et al. (CABI, Oxfordshire,2012), p. 99.
7) C. Schneider et al., Nat. Methods 9, 671 (2021).