Analysis of PEAM4, the pea AP1 functional homologue, supports a model for AP1‐like genes controlling both floral meristem and floral organ identity in different plant species

Abstract

SummaryAPETALA1 (AP1) and its homologue SQUAMOSA (SQUA) are key regulatory genes specifying¯oral meristem identity in the model plants Arabidopsis and Antirrhinum. Despite many similarities in their sequence, expression and functions, only AP1 appears to have the additional role of specifying sepal and petal identity. No true AP1/SQUA-functional homologues from any other plant species have been functionally studied in detail, therefore the question of how the different functions of AP1-like genes are conserved between species has not been addressed. We have isolated and characterized PEAM4, the AP1/SQUA-functional homologue from pea, a plant with a different¯oral morphology and in¯orescence architecture to that of Arabidopsis or Antirrhinum. PEAM4 encodes for a polypeptide 76% identical to AP1, but lacks the C-terminal prenylation motif, common to AP1 and SQUA, that has been suggested to control the activity of AP1. Nevertheless, constitutive expression of PEAM4 caused early¯owering in tobacco and Arabidopsis. In Arabidopsis, PEAM4 also caused in¯orescence-to-¯ower transformations similar to constitutive AP1 expression, and was able to rescue the¯oral organ defects of the strong ap1-1 mutant. Our results suggest that the control of both¯oral meristem and¯oral organ identity by AP1 is not restricted to Arabidopsis, but is extended to species with diverse¯oral morphologies, such as pea.

Identification and Characterization of Four Chrysanthemum MADS-Box Genes, Belonging to the APETALA1/FRUITFULL and SEPALLATA3 Subfamilies

“…5B). This early flowering and terminal flower phenotype has been reported for many AP1-like genes when overexpressed in Arabidopsis (Mandel and Yanofsky, 1995;Berbel et al, 2001), but also ectopic expression of MADS-box genes belonging to the SEP3 clade displays a similar phenotype (Honma and Goto, 2001;Ferrario et al, 2003). Therefore, we attempted to complement the mutant phenotype of the severe Arabidopsis ap1-1 mutant by overexpression of CDM111, which would confirm the functional equivalency of CDM111 and AP1.…”

VEGETATIVE1 is essential for development of the compound inflorescence in pea

“…The PsFULc complementary DNA was isolated from cDNA from inflorescence apices using PCR techniques; first, a 550-bp cDNA fragment was amplified by RT-PCR with primers derived from the M. truncatula FULc sequence and the remaining 5′-and 3′-fragments were amplified by PCR from a pea cDNA library 14 with primers from the vector and from the PsFULc cDNA fragment. To analyse the sequences of the PsFULc and PsSEP1 genes in the psfulc-2 mutant, several overlapping genomic fragments from each gene were amplified from genomic DNA from the mutant and from the parental wild type.…”

“…In wild-type plants, the floral transition is associated with transcriptional induction of DETERMINATE (DET) and PROLIFERATING INFLORESCENCE MERISTEM (PIM) [14][15][16][17] (Fig. 3a), which, like their Arabidopsis orthologues TERMINAL FLOWER 1 (TFL1) 18 and APETALA 1 (AP1) 19 , control the identity of the inflorescence and the floral meristems 14 expressed in wild-type plants, expression was not observed in veg1 (Fig. 3a), consistent with the absence of flowers or floral organs.…”

Floral Meristem Identity Genes Are Expressed during Tendril Development in Grapevine

“…In order to root the SQUA subfamily, Arabidopsis SEP1 (M55551), SEP2 (M55552), and SEP3 (AF015552) were used as outgroup. Berbel et al, 2001;Elo et al, 2001;Becker and Theissen, 2003).…”