Suppression of Arabidopsis flowering by near‐null magnetic field is mediated by auxin

We previously found that flowering of Arabidopsis was suppressed by near‐null magnetic field, which was related to cryptochrome. Auxin plays an important role in Arabidopsis flowering. To test whether auxin is involved in the suppression of Arabidopsis flowering by near‐null magnetic field, we detected auxin level and expressions of auxin transport and signaling genes in wild‐type Arabidopsis plants and cryptochrome double mutant, cry1/cry2, grown in near‐null magnetic field. We found that indole‐3‐acetic acid (IAA) level in roots of wild‐type plants in near‐null magnetic field was significantly increased compared with the local geomagnetic field control, while IAA level in rosettes of 33‐day‐old wild‐type plants in near‐null magnetic field was significantly lower than the control. Expressions of three auxin transporter genes, PIN1, PIN3, and PIN7, in wild‐type plants were upregulated by near‐null magnetic field. Transcript levels of transcriptional repressor genes, IAA1, IAA5, IAA6, IAA16, and IAA19, were significantly higher in wild‐type plants in near‐null magnetic field than in control plants. However, IAA level and expressions of all the detected genes in cry1/cry2 mutants in near‐null magnetic field were similar to controls. Our results suggest that near‐null magnetic field affects the distribution of auxin in Arabidopsis by transcriptional upregulation of auxin transporter genes, and that change in distribution of auxin and increased expressions of transcriptional repressor genes result in delay of flowering in Arabidopsis in near‐null magnetic field, which are mediated by cryptochrome. Bioelectromagnetics. 39:15–24, 2018. © 2017 Wiley Periodicals, Inc.