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Tracing the footprints of the ABCDE model of flowering in Phalaenopsis equestris (Schauer) Rchb.f. (Orchidaceae)
J Plant Biotechnol 2019;46:255-273
Published online December 31, 2019
© 2019 The Korean Society for Plant Biotechnology.

Himani · Thakku R. Ramkumar · Shivi Tyagi · Himanshu Sharma · Santosh K. Upadhyay · Jaspreet K. Sembi

Department of Botany, Panjab University, Chandigarh, India
Agronomy department, IFAS, University of Florida, Gainesville, FL, 32611, USA
IKG Punjab Technical University, Jalandhar
Correspondence to: e-mail:
Received August 13, 2019; Revised December 23, 2019; Accepted December 23, 2019.
cc This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Orchids are indispensable to the floriculture industry due to their unique floral organization. The flowers have two outer whorls of tepals including a lip (labellum), and two inner whorls, pollinia and gynostemiun (column). The floral organization and development is controlled at the molecular level, mainly by the MADS-box gene family, comprising homeotic genes divided into type I and type II groups. The type I group has four sub-groups, Mα, Mβ, Mγ, and Mδ, playing roles in seed, embryo, and female reproductive organ development; the type II group genes form classes A, B, C, D, and E, which are a part of the MIKCC subgroup with specific roles in florigenesis and organization. The coordinated functioning of these classes regulates the development of various floral whorls. The availability of genome and transcriptome sequence data for Phalaenopsis equestris offers an opportunity to validate the ABCDE model of flower development. Hence, this study sought to characterize the MADS-box gene family and elucidate of the ABCDE model. A total of 48 identified MADS-box proteins, including 20 type I [Mα (12), Mγ (8)] and 28 type II [MIKCC (27), MIKC* (1)] members, were characterized for physico-chemical features and domains and motifs organization. The exon-intron distribution and the upstream cis-regulatory elements in the promoter regions of MADS-box genes were also analysed. The discrete pace of duplication events in type I and type II genes suggested differential evolutionary constraints between groups. The correlation of spatio-temporal expression pattern with the presence of specific cis-regulatory elements and putative protein– protein interaction within the different classes of MADS-box gene family endorse the ABCDE model of floral development.
Keywords : MADS-box genes, Phalaenopsis equestris, Characterization, Expression, Flowering, ABCDE model

December 2019, 46 (4)
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Funding Information
  • Promotion of University Research and Scientific Excellence
  • Science and Engineering Research Board
  • Bio-CARe scheme
  • Early Career Research Award
  • CrossMark
  • Crossref TDM