| Fitness is associated with reproductive success. Initiating reproduction during optimal conditions may have an impact on fitness. Mechanisms to delay reproduction until the advent of favorable environmental conditions are likely to evolve. In Arabidopsis thaliana, members of the FLOWERING LOCUS C/MADS-AFFECTING FLOWERING Glade, repress the transition from vegetative to reproductive development under suboptimal temperature and photoperiod conditions. One of these genes, MADS-AFFECTING FLOWERING 2, represses flowering after a moderate cold treatment, but this response is not well-understood at the molecular level. This work used natural polymorphic MAF2 alleles and transgenic plants overexpressing splice variant forms of MAF2 to study the role of MAF2 and MAF2 alternative splicing in flowering time determinination. Natural polymorphimic alleles of MAF2 are common in the Arabidopsis thaliana accession collection and they are associated with early flowering. A sub-group of six MAF2 allele forms are characterized by an insertion, of varying lengths, of the adjacent paralogous gene, MADS-AFFECTING FLOWERING 3, into the last intron of the MAF2 coding region. Backcross five lines bearing four of these MAF2 insertion alleles were also associated with early flowering under long day conditions but were polymorphic for flowering time under a non-inductive, short day photoperiod. The backcross lines were unable to respond to a 16 day vernalization treatment compared to MAF2-Ler. Cold treatment modulated expression levels of MAF2 alternative transcripts in the Arabidopsis accessions Col and Ler and all studied polymorphic alleles of MAF2. In Col and Ler, this treatment enhanced expression of cDNA predicted to encode the full-length repressor. Data on the modulation of splice variant levels by cold conformed to observations of the flowering phenotype of maf2-1, a T-DNA knockout allele of MAF2. An over-expression study of MAF2 alternative splice variant forms showed that several splice variant forms can modulate flowering time, although the form that retained the capacity to instigate late flowering in T4, homozygous lines was MAF2 variant 1, the full length, cDNA form. This study found that the effect of cold on the splice variant profile of MAF2 may have functional consequences for flowering time determination of Arabidopsis thaliana..;Keywords: vernalization, alternative splicing, natural variation, populations, copy number variation, tandemly arrayed genes, flower development, flowering. |
