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Inefficient double-strand DNA break repair is associated with increased fasciation in Arabidopsis BRCA2 mutants.

Abe K, Osakabe K, Ishikawa Y, Tagiri A, Yamanouchi H, Takyuu T, Yoshioka T, Ito T, Kobayashi M, Shinozaki K, Ichikawa H, Toki S - J. Exp. Bot. (2009)

Bottom Line: An atbrca2a-1/atbrca2b-1 double mutant showed an additive increase in sensitivity to genotoxic stresses compared to each single mutant.In addition, it was found that atbrca2 mutant plants displayed fasciation and abnormal phyllotaxy phenotypes with low incidence, and that the ratio of plants exhibiting these phenotypes is increased by gamma-irradiation.Moreover, it was found that shoot apical meristems of the atbrca2a-1/atbrca2b-1 double mutant show altered cell cycle progression.

View Article: PubMed Central - PubMed

Affiliation: Division of Plant Sciences, National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602, Japan.

ABSTRACT
BRCA2 is a breast tumour susceptibility factor with functions in maintaining genome stability through ensuring efficient double-strand DNA break (DSB) repair via homologous recombination. Although best known in vertebrates, fungi, and higher plants also possess BRCA2-like genes. To investigate the role of Arabidopsis BRCA2 genes in DNA repair in somatic cells, transposon insertion mutants of the AtBRCA2a and AtBRCA2b genes were identified and characterized. atbrca2a-1 and atbrca2b-1 mutant plants showed hypersensitivity to genotoxic stresses compared to wild-type plants. An atbrca2a-1/atbrca2b-1 double mutant showed an additive increase in sensitivity to genotoxic stresses compared to each single mutant. In addition, it was found that atbrca2 mutant plants displayed fasciation and abnormal phyllotaxy phenotypes with low incidence, and that the ratio of plants exhibiting these phenotypes is increased by gamma-irradiation. Interestingly, these phenotypes were also induced by gamma-irradiation in wild-type plants. Moreover, it was found that shoot apical meristems of the atbrca2a-1/atbrca2b-1 double mutant show altered cell cycle progression. These data suggest that inefficient DSB repair in the atbrca2a-1/atbrca2b-1 mutant leads to disorganization of the programmed cell cycle of apical meristems.

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(A) Sensitivity to cisplatin of single mutants atbrca2a-1 and atbrca2b-1, and the double mutant atbrca2a-1/atbrca2b-1. Imbibed seeds were plated on MS agar medium containing 0–50 μM cisplatin. The numbers of true leaves in wild type (Nossen) and mutant plants were counted 14 d after plating. Data represent the mean ±SE of 50 plants in each group from three experiments. (B, C) Sensitivity of AtBRCA2 mutants to γ-irradiation. (B) Imbibed seeds (4 d at 4 °C) were irradiated with increasing doses of 60Co γ-rays. After γ-irradiation, the seeds were immediately plated on MS agar medium. The number of true leaves was counted 10 d after irradiation, and the average number of leaves was calculated according to Harlow et al. (1994). Data represent the mean ±SE of 34 plants in each group from three experiments. (C) Fourteen-day-old plantlets [upper panels: wild type (Nossen), lower panels: atbrca2a-1/atbrca2b-1 double mutant plants] after γ-irradiation (0, 300, 600 Gy).
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fig1: (A) Sensitivity to cisplatin of single mutants atbrca2a-1 and atbrca2b-1, and the double mutant atbrca2a-1/atbrca2b-1. Imbibed seeds were plated on MS agar medium containing 0–50 μM cisplatin. The numbers of true leaves in wild type (Nossen) and mutant plants were counted 14 d after plating. Data represent the mean ±SE of 50 plants in each group from three experiments. (B, C) Sensitivity of AtBRCA2 mutants to γ-irradiation. (B) Imbibed seeds (4 d at 4 °C) were irradiated with increasing doses of 60Co γ-rays. After γ-irradiation, the seeds were immediately plated on MS agar medium. The number of true leaves was counted 10 d after irradiation, and the average number of leaves was calculated according to Harlow et al. (1994). Data represent the mean ±SE of 34 plants in each group from three experiments. (C) Fourteen-day-old plantlets [upper panels: wild type (Nossen), lower panels: atbrca2a-1/atbrca2b-1 double mutant plants] after γ-irradiation (0, 300, 600 Gy).

Mentions: Both single mutants were hypersensitive to cisplatin compared to wild-type (Nossen) (Fig. 1A). Moreover, the atbrca2a-1/atbrca2b-1 double mutant showed an additive increase in sensitivity to cisplatin treatment compared with that of the corresponding single mutants and wild-type plants (Fig. 1A). The effect was particularly apparent following treatment with 30 μM cisplatin, when the number of true leaves appearing in the double mutant plant was close to zero, single mutant plants produced an average of about 1.2–1.5 leaves, and wild-type plants about 2.4 leaves (Fig. 1A).


Inefficient double-strand DNA break repair is associated with increased fasciation in Arabidopsis BRCA2 mutants.

Abe K, Osakabe K, Ishikawa Y, Tagiri A, Yamanouchi H, Takyuu T, Yoshioka T, Ito T, Kobayashi M, Shinozaki K, Ichikawa H, Toki S - J. Exp. Bot. (2009)

(A) Sensitivity to cisplatin of single mutants atbrca2a-1 and atbrca2b-1, and the double mutant atbrca2a-1/atbrca2b-1. Imbibed seeds were plated on MS agar medium containing 0–50 μM cisplatin. The numbers of true leaves in wild type (Nossen) and mutant plants were counted 14 d after plating. Data represent the mean ±SE of 50 plants in each group from three experiments. (B, C) Sensitivity of AtBRCA2 mutants to γ-irradiation. (B) Imbibed seeds (4 d at 4 °C) were irradiated with increasing doses of 60Co γ-rays. After γ-irradiation, the seeds were immediately plated on MS agar medium. The number of true leaves was counted 10 d after irradiation, and the average number of leaves was calculated according to Harlow et al. (1994). Data represent the mean ±SE of 34 plants in each group from three experiments. (C) Fourteen-day-old plantlets [upper panels: wild type (Nossen), lower panels: atbrca2a-1/atbrca2b-1 double mutant plants] after γ-irradiation (0, 300, 600 Gy).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2692019&req=5

fig1: (A) Sensitivity to cisplatin of single mutants atbrca2a-1 and atbrca2b-1, and the double mutant atbrca2a-1/atbrca2b-1. Imbibed seeds were plated on MS agar medium containing 0–50 μM cisplatin. The numbers of true leaves in wild type (Nossen) and mutant plants were counted 14 d after plating. Data represent the mean ±SE of 50 plants in each group from three experiments. (B, C) Sensitivity of AtBRCA2 mutants to γ-irradiation. (B) Imbibed seeds (4 d at 4 °C) were irradiated with increasing doses of 60Co γ-rays. After γ-irradiation, the seeds were immediately plated on MS agar medium. The number of true leaves was counted 10 d after irradiation, and the average number of leaves was calculated according to Harlow et al. (1994). Data represent the mean ±SE of 34 plants in each group from three experiments. (C) Fourteen-day-old plantlets [upper panels: wild type (Nossen), lower panels: atbrca2a-1/atbrca2b-1 double mutant plants] after γ-irradiation (0, 300, 600 Gy).
Mentions: Both single mutants were hypersensitive to cisplatin compared to wild-type (Nossen) (Fig. 1A). Moreover, the atbrca2a-1/atbrca2b-1 double mutant showed an additive increase in sensitivity to cisplatin treatment compared with that of the corresponding single mutants and wild-type plants (Fig. 1A). The effect was particularly apparent following treatment with 30 μM cisplatin, when the number of true leaves appearing in the double mutant plant was close to zero, single mutant plants produced an average of about 1.2–1.5 leaves, and wild-type plants about 2.4 leaves (Fig. 1A).

Bottom Line: An atbrca2a-1/atbrca2b-1 double mutant showed an additive increase in sensitivity to genotoxic stresses compared to each single mutant.In addition, it was found that atbrca2 mutant plants displayed fasciation and abnormal phyllotaxy phenotypes with low incidence, and that the ratio of plants exhibiting these phenotypes is increased by gamma-irradiation.Moreover, it was found that shoot apical meristems of the atbrca2a-1/atbrca2b-1 double mutant show altered cell cycle progression.

View Article: PubMed Central - PubMed

Affiliation: Division of Plant Sciences, National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602, Japan.

ABSTRACT
BRCA2 is a breast tumour susceptibility factor with functions in maintaining genome stability through ensuring efficient double-strand DNA break (DSB) repair via homologous recombination. Although best known in vertebrates, fungi, and higher plants also possess BRCA2-like genes. To investigate the role of Arabidopsis BRCA2 genes in DNA repair in somatic cells, transposon insertion mutants of the AtBRCA2a and AtBRCA2b genes were identified and characterized. atbrca2a-1 and atbrca2b-1 mutant plants showed hypersensitivity to genotoxic stresses compared to wild-type plants. An atbrca2a-1/atbrca2b-1 double mutant showed an additive increase in sensitivity to genotoxic stresses compared to each single mutant. In addition, it was found that atbrca2 mutant plants displayed fasciation and abnormal phyllotaxy phenotypes with low incidence, and that the ratio of plants exhibiting these phenotypes is increased by gamma-irradiation. Interestingly, these phenotypes were also induced by gamma-irradiation in wild-type plants. Moreover, it was found that shoot apical meristems of the atbrca2a-1/atbrca2b-1 double mutant show altered cell cycle progression. These data suggest that inefficient DSB repair in the atbrca2a-1/atbrca2b-1 mutant leads to disorganization of the programmed cell cycle of apical meristems.

Show MeSH
Related in: MedlinePlus