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

• Published in: The Plant journal : for cell and molecular biology 2001-02, Vol.25 (4), p.441-451
• Main Authors: Berbel, Ana, Navarro, Cristina, Ferrándiz, Cristina, Cañas, Luis Antonio, Madueño, Francisco, Beltrán, José‐Pío
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Amino Acid Sequence; Antirrhinum; AP1 gene; APETALA1; Arabidopsis; A‐function; Base Sequence; Biological and medical sciences; Biology and morphogenesis of the reproductive apparatus. Photoperiodism, vernalisation; DNA Primers; Economic plant physiology; floral initiation; Flowering, floral biology, reproduction patterns; Fundamental and applied biological sciences. Psychology; Genotype; Growth and development; Homeodomain Proteins - chemistry; Homeodomain Proteins - genetics; Homeodomain Proteins - physiology; In Situ Hybridization; Meristem - growth & development; Molecular Sequence Data; pea floral development; PEAM4 gene; Phenotype; pim mutant; Pisum sativum - genetics; Plant physiology and development; Plant Proteins - chemistry; Plant Proteins - genetics; Plant Proteins - physiology; Sequence Homology, Amino Acid; Species Specificity; SQUAMOSA; SQUAMOSA gene; Vegetative and sexual reproduction, floral biology, fructification
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313x.2001.00974.x

Summary APETALA1 (AP1) and its homologue SQUAMOSA (SQUA) are key regulatory genes specifying floral 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 floral morphology and inflorescence 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 flowering in tobacco and Arabidopsis. In Arabidopsis, PEAM4 also caused inflorescence‐to‐flower transformations similar to constitutive AP1 expression, and was able to rescue the floral organ defects of the strong ap1‐1 mutant. Our results suggest that the control of both floral meristem and floral organ identity by AP1 is not restricted to Arabidopsis, but is extended to species with diverse floral morphologies, such as pea.