Near-Null Magnetic Field Suppresses Fruit Growth in Arabidopsis.

We previously found that a near-null magnetic field affected reproductive growth in Arabidopsis under white light. To test whether the effect of a near-null magnetic field on fruit growth of Arabidopsis is related to cryptochrome, we grew wild-type Arabidopsis and cryptochrome double mutant, cry1/cry2, in a near-null magnetic field under blue light. We found that fruit growth of wild-type Arabidopsis instead of the cry1/cry2 mutant was suppressed by the near-null magnetic field. Furthermore, gibberellin (GA) levels of GA4 , GA9 , GA34 , and GA51 in fruits of wild-type plants in the near-null magnetic fields were significantly lower than local geomagnetic field controls. However, in cry1/cry2 mutants, levels of the four detected GAs in fruits in the near-null magnetic fields did not differ significantly from controls. Expressions of GA20-oxidase (GA20ox) genes (GA20ox1 and GA20ox2) and GA3-oxidase (GA3ox) genes (GA3ox1 and GA3ox3) in fruits of wild-type plants rather than cry1/cry2 mutants were downregulated by the near-null magnetic field. In contrast, expressions of GA2-oxidase (GA2ox) genes and GA signaling genes were not affected by the near-null magnetic field. These results indicate that suppression of fruit growth by the near-null magnetic field is mediated by cryptochrome and that GAs are involved in the regulation of fruit growth by the near-null magnetic field.