Expression patterns ofPassiflora edulis APETALA1/FRUITFULLhomologues shed light onto tendril and corona identities.
BACKGROUND
Passiflora(passionflowers) makes an excellent model for studying plant evolutionary development. They are mostly perennial climbers that display axillary tendrils, which are believed to be modifications of the inflorescence. Passionflowers are also recognized by their unique flower features, such as the extra whorls of floral organs composed of corona filaments and membranes enclosing the nectary. Although some work onPassifloraorgan ontogeny has been done, the developmental identity of bothPassifloratendrils and the corona is still controversial. Here, we combined ultrastructural analysis and expression patterns of the flower meristem and floral organ identity genes of the MADS-boxAP1/FULclade to reveal a possible role for these genes in the generation of evolutionary novelties inPassiflora.


RESULTS
We followed the development of structures arising from the axillary meristem from juvenile to adult phase inP. edulis. We further assessed the expression pattern ofP. edulis AP1/FULhomologues (PeAP1andPeFUL), by RT-qPCR and in situ hybridization in several tissues, correlating it with the developmental stages ofP. edulis.PeAP1is expressed only in the reproductive stage, and it is highly expressed in tendrils and in flower meristems from the onset of their development.PeAP1is also expressed in sepals, petals and in corona filaments, suggesting a novel role forPeAP1in floral organ diversification.PeFULpresented a broad expression pattern in both vegetative and reproductive tissues, and it is also expressed in fruits.


CONCLUSIONS
Our results provide new molecular insights into the morphological diversity in the genusPassiflora. Here, we bring new evidence that tendrils are part of thePassiflorainflorescence. This points to the convergence of similar developmental processes involving the recruitment of genes related to flower identity in the origin of tendrils in different plant families. The data obtained also support the hypothesis that the corona filaments are likelysui generisfloral organs. Additionally, we provide an indication thatPeFULacts as a coordinator of passionfruit development.
Departamento de Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas, Rua Monteiro Lobato, 255, 13083-862 Campinas, SP Brazil.|Institute of Molecular Plant Sciences, University of Edinburgh, Max Born Crescent, King's Buildings, Edinburgh, EH9 3BF UK.
Livia C T
LCT
Scorza
Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Rua do Matão 277, 05508-090 São Paulo, SP Brazil.
Jose
J
Hernandes-Lopes
Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Rua do Matão 277, 05508-090 São Paulo, SP Brazil.
Gladys F A
GFA
Melo-de-Pinna
Departamento de Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas, Rua Monteiro Lobato, 255, 13083-862 Campinas, SP Brazil.
Marcelo C
MC
Dornelas
APETALA1; Corona; FRUITFULL; Flower meristem; MADS-box; Passiflora edulis; Passifloraceae; Tendril