Project description:Flowering of perennial Arabis alpina, is differentially regulated on primary and axillary shoots. Although contributions of vernalization and aging pathways have been analyzed, those of photoperiodic flowering genes CONSTANS (CO), FLOWERING LOCUS T (FT), and TWIN-SISTER OF FT (TSF) remain unexplored. CRISPR-Cas9 mutations in AaCO and AaFT/TWIN SISTER OF FT-LIKE (TSFL) were recovered. Aaco and Aaft/tsfl mutants in pep1 background were scored for flowering time, inflorescence branching and floral phenotypes under long (LD) or short days (SD) and after vernalization. RNAseq data on primary and axillary branches were compared. AaCO activates AaFT/TSFL transcription in leaves, and Aaco and Aaft tsfl mutations delay flowering under LDs. Axillary branches flowered in Aaco mutants but not in Aaft tsfl mutants. Both lacked inflorescence branches and flowers on the primary shoot under LDs. However, Aaft tsfl mutants produced some flowers after vernalization, and Aaco a few in SDs. RNAseq identified genes responsive to AaFT, TSFL and AaCO on the primary shoot and in axillary branches. Therefore, AaCO-AaFT promote flowering of A. alpina under LDs, but with distinct roles in axillary branch flowering. Both genes are required for inflorescence branching and flower formation on the primary shoot. The complex role of the CO-FT module in inflorescence architecture may underlie the polycarpic, perennial life history of A. alpina.
Project description:Polycarpic perennials maintain vegetative growth after flowering. PERPETUAL FLOWERING 1 (PEP1), the orthologue of FLOWERING LOCUS C (FLC) inArabis alpina regulates flowering and contributes to polycarpy in a vernalisation-dependent pathway. pep1 mutants do not require vernalisation to flower and have reduced return to vegetative growth as all of their axillary branches become reproductive. To identify additional genes that regulate flowering and contribute to perennial traits we performed an enhancer screen of pep1. Using mapping-by-sequencing, we cloned a mutant (enhancer of pep1-055, eop055), performed transcriptome analysis and physiologically characterised the role it plays on perennial traits in an introgression line carrying the eop055 mutation and a functional PEP1 wild-type allele. eop055 flowers earlier than pep1 and carries a lesion in the A. alpina orthologue of the APETALA2 (AP2)-like gene, TARGET OF EAT2 (AaTOE2). AaTOE2 is a floral repressor and acts upstream of SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 5 (AaSPL5). In the wild-type background, which requires cold treatment to flower, AaTOE2 regulates the age-dependent response to vernalisation. In addition, AaTOE2 ensures the maintenance of vegetative growth by delaying axillary meristem initiation and repressing flowering of axillary buds before and during cold exposure. We conclude that AaTOE2 is instrumental in fine tuning different developmental traits in the perennial life cycle of A. alpina.
Project description:Polycarpic perennials maintain vegetative growth after flowering. PERPETUAL FLOWERING 1 (PEP1), the orthologue of FLOWERING LOCUS C (FLC) inArabis alpina regulates flowering and contributes to polycarpy in a vernalisation-dependent pathway. pep1 mutants do not require vernalisation to flower and have reduced return to vegetative growth as all of their axillary branches become reproductive. To identify additional genes that regulate flowering and contribute to perennial traits we performed an enhancer screen of pep1. Using mapping-by-sequencing, we cloned a mutant (enhancer of pep1-055, eop055), performed transcriptome analysis and physiologically characterised the role it plays on perennial traits in an introgression line carrying the eop055 mutation and a functional PEP1 wild-type allele. eop055 flowers earlier than pep1 and carries a lesion in the A. alpina orthologue of the APETALA2 (AP2)-like gene, TARGET OF EAT2 (AaTOE2). AaTOE2 is a floral repressor and acts upstream of SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 5 (AaSPL5). In the wild-type background, which requires cold treatment to flower, AaTOE2 regulates the age-dependent response to vernalisation. In addition, AaTOE2 ensures the maintenance of vegetative growth by delaying axillary meristem initiation and repressing flowering of axillary buds before and during cold exposure. We conclude that AaTOE2 is instrumental in fine tuning different developmental traits in the perennial life cycle of A. alpina.
Project description:The floral repressor APETALA2 (AP2) in Arabidopsis regulates flowering through the age pathway. The AP2 ortholog in the alpine perennial Arabis alpina, PERPETUAL FLOWERING 2 (PEP2), was previously reported to control flowering through the vernalization pathway via enhancing the expression of another floral repressor PERPETUAL FLOWERING 1 (PEP1), the ortholog of Arabidopsis FLOWERING LOCUS C (FLC). However, PEP2 also regulates flowering independently of PEP1. To characterize the function of PEP2, we analyzed the transcriptomes of pep2 and pep1 mutants. The majority of differentially expressed genes were detected between pep2 and the wild type or between pep2 and pep1, highlighting the importance of the PEP2 role that is independent of PEP1. Here, we demonstrate that PEP2 activity prevents the up-regulation of the A. alpina floral meristem identity genes FRUITFUL (AaFUL), LEAFY (AaLFY), and APETALA1 (AaAP1), ensuring floral commitment during vernalization. Young pep2 seedlings respond to vernalization, suggesting that PEP2 regulates the age-dependent response to vernalization independently of PEP1. The major role of PEP2 through the PEP1-dependent pathway takes place after vernalization, when it facilitates PEP1 activation both in the main shoot apex and in axillary branches. These multiple roles of PEP2 in the vernalization response contribute to the A. alpina life cycle.