Photoperiod-dependent floral reversion in the natural allopolyploid Arabidopsis suecica

Flower reversion is the result of genetic or environmental effects that reverse developmental steps in the transition from the vegetative to the reproductive phase in plants. Here, we describe peculiar floral abnormalities, homeotic conversions, and flower reversion in several wild-type accessions of the natural allopolyploid Arabidopsis suecica. Microscopy was used to illustrate the phenotype in detail and we experimented with varying photoperiod lengths to establish whether or not the phenotype was responsive to the environment. We also profiled the transcriptional activity of several floral regulator genes during flower reversion using real-time PCR. We showed that the frequency of floral reversion was affected by day length and the position of the flower along the inflorescence axis. In reverting flowers we found unusual gene expression patterns of floral promoters and inflorescence maintenance genes, including lower mRNA levels of AGAMOUS-LIKE-24 (AGL-24), APETALA1 (AP1), and SHORT VEGETATIVE PHASE (SVP), and higher mRNA levels of SUPRESSOR OF CONSTANS1 (SOC1) compared with normal flowers. We conclude that the floral reversion frequency in A. suecica is susceptible to photoperiod changes, and that the floral abnormalities coincide with the competing expression of floral promoters and floral repressors in reverting floral tissue.