PERPETUAL FLOWERING2coordinates the vernalization response and perennial flowering inArabis alpina

Abstract

TITLE 1 PERPETUAL FLOWERING2 coordinates the vernalization response and perennial flowering in 2 Arabis alpina 3 4 5 RUNNING TITLE 6 PEP2 coordinates flowering in response to vernalization 7 8 HIGHLIGHT 9The Arabis alpina APETALA2 orthologue, PERPETUAL FLOWERING2, regulates the age-10 dependent response to vernalization and it is required to facilitate the activation of the A. 11 alpina FLOWERING LOCUS C after vernalization. 12 13 ABSTRACT 14 The floral repressor APETALA2 (AP2) in Arabidopsis regulates flowering through the age 15 pathway. The AP2 orthologue in the alpine perennial Arabis alpina, PERPETUAL FLOWERING 16 2 (PEP2), was previously reported to regulate flowering through the vernalization pathway by 17 enhancing the expression of another floral repressor PERPETUAL FLOWERING 1 (PEP1), the 18 orthologue of Arabidopsis FLOWERING LOCUS C (FLC). However, PEP2 also regulates flowering 19 independently of PEP1. To characterize the function of PEP2 we analyzed the transcriptomes 20 of pep2 and pep1 mutants. The majority of differentially expressed genes were detected 21 between pep2 and the wild type or between pep2 and pep1, highlighting the importance of 22 the PEP2 role that is independent of PEP1. Here we demonstrate that PEP2 prevents the 23 upregulation of the A. alpina floral meristem identity genes FRUITFUL (AaFUL), LEAFY (AaLFY) 24 and APETALA1 (AaAP1) which ensure floral commitment during vernalization. Young pep2 25 seedlings respond to vernalization, suggesting that PEP2 regulates the age-dependent 26 response to vernalization independently of PEP1. The major role of PEP2 through the PEP1-27 dependent pathway takes place after vernalization, when it facilitates PEP1 activation both in 28 4 the main shoot apex and in the axillary branches. These multiple roles of PEP2 in vernalization 29 response contribute to the A. alpina life-cycle. 30 31 KEY WORDS: APETALA2, AP2, juvenility, FLOWERING LOCUS C, FLC, perennial, PERPETUAL 32 FLOWERING 1, PEP1, PEP2, vernalization 33 34 ABBREVIATIONS: 35 DAG: Days after germination 36 LDs: Long days 37 SDs: Short days 38 39box transcription factor FLOWERING LOCUS C (FLC) is the major regulator of flowering in 56 response to vernalization (Michaels and Amasino, 1999; Sheldon et al., 2000). FLC 57 transcriptionally regulates floral integrator genes such as SUPPRESSOR OF OVEREXPRESSION 58 OF CONSTANS1 (SOC1), and genes involved in the age pathway, suggesting an interplay 59 between these two pathways (Deng et al., 2011; Mateos et al., 2017). Comparative studies 60 between Arabidopsis and the alpine perennial Arabis alpina demonstrated that the FLC 61 orthologue in A. alpina, PERPETUAL FLOWERING1 (PEP1), also regulates flowering in response 62 to vernalization. In addition, PEP1 contributes to the perennial growth habit by repressing 63 flowering in a subset of axillary meristems after vernalization (Lazaro et al., 2018; Wang et al., 64 2009). Flower buds in A. alpina are formed during prolonged exposure to vernalizing 65 conditions. The length of vernalization deter...

Beyond flowering time: diverse roles of an APETALA2‐like transcription factor in shoot architecture and perennial traits

“…To understand the function of AaTOE2 in A. alpina we introgressed the Aatoe2 allele into the wild‐type background by crossing eop055 with Pajares and selecting an Aatoe2 _IL homozygous for Aatoe2 which contained a functional PEP1 . We have previously shown that AP2 in A. alpina (PEP2) regulates flowering and perennial traits through the age pathway and plays a role in the vernalisation pathway by enhancing PEP1 mRNA levels (Lázaro et al ., 2019). The pep2‐1 mutant does not require cold treatment to flower and has reduced PEP1 mRNA levels compared with the wild‐type (Bergonzi et al ., 2013).…”

“…The effect of the age pathway in A. alpina is obvious after cold treatment (Wang et al ., 2011; Bergonzi et al ., 2013; Hyun et al ., 2019; Lázaro et al ., 2019). To test whether AaTOE2 regulated the age‐dependent response to vernalisation, we vernalised 3‐wk‐old wild‐type and Aatoe2 _IL seedlings for 12 wk and tested whether they flowered (Fig.…”

“…AaSPL5, probably, does not participate in this differential AaTOE2/ miR172 feedback. The A. alpina AP2 (PEP2) regulates the fate of V3 branches by ensuring the upregulation of PEP1 mRNA levels after vernalisation (Lázaro et al ., 2019). In this respect, AaTOE2 differs from PEP2 as it does not influence PEP1 expression levels.…”

“…Nevertheless, AaTOE2 has an effect on flowering only in vernalised plants suggesting that PEP1 plays a prominent role repressing flowering in parallel to AaTOE2. PEP2 regulates flowering through the age and the vernalisation pathways (Lázaro et al ., 2019). Thus, although AaTOE2 does not influence PEP1 mRNA levels, it could have overlapping functions with PEP2 through the age pathway.…”

“…Quantitative PCRs to follow gene expression were carried out as described in Lázaro et al . (2019) and for miRNAs as described in Bergonzi et al . (2013).…”