Albani, M. C. | Search bioRxiv

bioRxiv2019

Flowering behaviour in Arabis alpina ensures the maintenance of a perennating dormant bud bank

Arabis alpina, similar to woody perennials, has a complex architecture with a zone of axillary vegetative branches and a zone of dormant buds that serve as perennating organs. We show that floral development during vernalization is the key for shaping the dormant bud zone by facilitating a synchronized and rapid growth after vernalization and thereby causing an increase in auxin response and transport and endogenous indole-3-acetic acid (IAA) levels in the stem. Floral development during vernalization is associated with the development of axillary buds in subapical nodes. Our transcriptome analysis indicated that these buds are not dormant during vernalization but only attain sustained growth after the return to warm temperatures. Floral and subapical vegetative branches grow after vernalization and inhibit the development of the buds below. Dormancy in these buds is regulated across the A. alpina life cycle by low temperatures and by apical dominance in a BRANCHED 1-dependent mechanism.

plant biology↗

bioRxiv2018

PERPETUAL FLOWERING2 coordinates the vernalization response and perennial flowering in Arabis alpina

The floral repressor APETALA2 (AP2) in Arabidopsis regulates flowering through the age pathway. The AP2 orthologue in the alpine perennial Arabis alpina, PERPETUAL FLOWERING 2 (PEP2), was previously reported to regulate flowering through the vernalization pathway by enhancing the expression of another floral repressor PERPETUAL FLOWERING 1 (PEP1), the orthologue 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 prevents the upregulation of the A. alpina floral meristem identity genes FRUITFUL (AaFUL), LEAFY (AaLFY) and APETALA1 (AaAP1) which ensure 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 the axillary branches. These multiple roles of PEP2 in vernalization response contribute to the A. alpina life-cycle.\n\nHIGHLIGHTThe Arabis alpina APETALA2 orthologue, PERPETUAL FLOWERING2, regulates the age-dependent response to vernalization and it is required to facilitate the activation of the A. alpina FLOWERING LOCUS C after vernalization.

plant biology↗