Petunia Ap2-like Genes and Their Role in Flower and Seed Development

Abstract

We have isolated three Apetala2 ( Ap2 )-like genes from petunia and studied their expression patterns by in situ hybridization. PhAp2A has a high sequence similarity to the A function gene Ap2 from Arabidopsis and a similar expression pattern during flower development, suggesting that they are cognate orthologs. PhAp2B and PhAp2C encode for AP2-like proteins that belong to a different subgroup of the AP2 family of transcription factors and exhibit divergent, nearly complementary expression patterns during flower development compared with PhAp2A . In contrast, all three PhAp2 genes are strongly expressed in endosperm. The phenotype of the petunia A-type mutant blind cannot be attributed to mutations in the petunia Ap2 homologs identified in this study, and reverse genetics strategies applied to identify phap2a mutants indicate that PhAp2A might not be essential for normal perianth development in petunia. Nevertheless, we show that PhAp2A is capable of restoring the homeotic transformations observed in flowers and seed of the ap2-1 mutant of Arabidopsis. Although the interspecific complementation proves that PhAp2A encodes a genuine Ap2 ortholog from petunia, additional factors may be involved in the control of perianth identity in this species.

Analysis of gymnosperm two-AP2-domain-containing genes

“…PtAP2L2 is expressed in both female and male cones. In contrast, IDS1 and PhAp2B are expressed much more strongly in stamens rather than in carpels, where little or no expression is observed (Chuck et al 1998;Maes et al 2001).…”

“…The resulting gene tree showed that the AP2 subfamily consists of ANT homologous genes and AP2 homologous genes, and that PtANTL1 clusters with ANT with moderately high bootstrap values. PtAP2L1 also clusters with A. thaliana AP2 (Jofuku et al 1994) and NP 201519, P. hybrida PhAp2A (Maes et al 2001), Malus domestica AHAP2, Pisum sativum AAK14326, and Picea abies PaAP2L1 (Vahala et al 2001), with moderately high bootstrap values. In contrast, the phylogenetic relationship between PtAP2L2 and the other AP2 homologous genes was unclear, and could not be clarified by a gene tree constructed with only AP2 homologous genes (data not shown).…”

“…Mutant analyses revealed that AP2 is also involved in ovule morphogenesis, during which abnormal seed coats and the formation of distinct carpel-sepal and filamentous ovules were observed (Jofuku et al 1994;Modrusan et al 1994). PhAp2A is expressed in the ovule primordium, and later in the funiculus and integument (Maes et al 2001).…”

“…expression was examined by RNA gel blot containing 1 g poly(A)+ RNA and in situ hybridization (Chuck et al 1998) b Glossy15 expression was examined by RNA gel blot analysis of poly(A)+ RNA, RT-PCR and Southern hybridization (Moose and Sisco 1996) c APETALA2 expression was examined by RNA gel blot analysis of poly(A)+ RNA and in situ hybridization (Jofuku et al 1994) d PhAp2A, PhAp2B, and PhAp2C expressions were examined by in situ hybridization (Maes et al 2001) e…”

AFLP maps of Petunia hybrida: building maps when markers cluster

“…Martin and Gerats 1993;Colombo et al 1997;Mol et al 1998;Robbins et al 2000). Over the past decade both forward Van den Broeck et al 1998) and reverse Maes et al 1999Maes et al , 2001 genetic approaches have been developed and applied successfully to recover mutant alleles and characterise mutant phenotypes in petunia.…”