Abstract Detail

Development and Structure

Martínez-Salazar, Sebastián [1], González, Favio [2], Alzate, Juan Fernando [3], Pabon Mora, Natalia [1].

Molecular framework underlying floral bilateral symmetry and nectar spur development in Tropaeolum, an atypical member of the Brassicales.

Nectar spurs are key innovations associated with elaborate pollination mechanisms that have evolved independently several times across angiosperms. Spur formation can shift the floral symmetry from radial to bilateral, as it is the case in Tropaeolaceae, the only member of the Brassicales with floral spurs. The genetic mechanisms underlying both spur development and bilateral symmetry in the family have not yet been investigated. We first studied flower development and morphoanatomy of Tropaeolum longifolium. We also generated reference transcriptomes for T. longifolium and T. majus and isolated all candidate genes involved in adaxial-abaxial differential growth during spur formation, namely CYCLOIDEA-like (CYC), CINCINNATA-like (CIN), RADIALIS-like (RAD), DIVARICATA-like (DIV) and class I KNOTTED1-LIKE HOMEOBOX (KNOX1) genes. Finally, we evaluated the evolution of the targeted genes across Brassicales and examined their expression in dissected floral parts. Our observations show that intercalary growth at the common base of sepals and petals forms a floral tube in T. longifolium. The spur is an outgrowth from the adaxial region of the tube, lined up with the medial sepal. We also identified Tropaeolum-specific duplications in the CINCINNATA3 (CIN3) and SHOOT MERISTEMLESS (STM) gene lineages, which code for transcription factors critical for spur formation in other taxa. Out of the 20 candidate genes that we studied, three seem pivotal for the extreme adaxial-abaxial asymmetry of the floral tube, namely, TlTCP4L2 restricted to the adaxial side where the spur is formed, and TlTCP12 and TlSTM1 to the abaxial side, which lacks a spur. The overlapping expression of cell division markers with these genes will allow us to better test their contribution to the differential growth of the floral tube.

1 - Universidad de Antioquia, Instituto de Biología, Calle 70 #52-21, Medellín, ANT, 050010, Colombia
2 - Universidad Nacional de Colombia, Instituto de Ciencias Naturales, AA 7495, Bogotá, 111321, Colombia
3 - Universidad de Antioquia, Centro Nacional de Secuenciación Genómica, Carrera 53 #61-30, Medellín, ANT, 050010, Colombia

Keywords:
Bilateral flower symmetry
CINCINNATA
CYCLOIDEA
evo-devo
floral tube
KNOX
nectar spur development.

Presentation Type: Oral Paper
Session: DS2, Development and Structure II
Location: /
Date: Wednesday, July 21st, 2021
Time: 10:00 AM(EDT)
Number: DS2001
Abstract ID:497
Candidate for Awards:Katherine Esau Award