Genome-Wide Identification and Analysis of the APETALA2 (AP2) Transcription Factor in Dendrobium officinale

Abstract

The APETALA2 (AP2) transcription factors (TFs) play crucial roles in regulating development in plants. However, a comprehensive analysis of the AP2 family members in a valuable Chinese herbal orchid, Dendrobium officinale, or in other orchids, is limited. In this study, the 14 DoAP2 TFs that were identified from the D. officinale genome and named DoAP2-1 to DoAP2-14 were divided into three clades: euAP2, euANT, and basalANT. The promoters of all DoAP2 genes contained cis-regulatory elements related to plant development and also responsive to plant hormones and stress. qRT-PCR analysis showed the abundant expression of DoAP2-2, DoAP2-5, DoAP2-7, DoAP2-8 and DoAP2-12 genes in protocorm-like bodies (PLBs), while DoAP2-3, DoAP2-4, DoAP2-6, DoAP2-9, DoAP2-10 and DoAP2-11 expression was strong in plantlets. In addition, the expression of some DoAP2 genes was down-regulated during flower development. These results suggest that DoAP2 genes may play roles in plant regeneration and flower development in D. officinale. Four DoAP2 genes (DoAP2-1 from euAP2, DoAP2-2 from euANT, and DoAP2-6 and DoAP2-11 from basal ANT) were selected for further analyses. The transcriptional activation of DoAP2-1, DoAP2-2, DoAP2-6 and DoAP2-11 proteins, which were localized in the nucleus of Arabidopsis thaliana mesophyll protoplasts, was further analyzed by a dual-luciferase reporter gene system in Nicotiana benthamiana leaves. Our data showed that pBD-DoAP2-1, pBD-DoAP2-2, pBD-DoAP2-6 and pBD-DoAP2-11 significantly repressed the expression of the LUC reporter compared with the negative control (pBD), suggesting that these DoAP2 proteins may act as transcriptional repressors in the nucleus of plant cells. Our findings on AP2 genes in D. officinale shed light on the function of AP2 genes in this orchid and other plant species.

Genome-wide identification and characterization of AP2/ERF gene superfamily during flower development in Actinidia eriantha

“…For instance, in ‘ABC’ model of flower development, APETALA2 ( AP2 ) as an A-class gene took part in flower formation [ 17 ]. Recently, researchers have found that the expressions of two DoAP2 genes ( DoAP2–8 and DoAP2–10 ) were down-regulated and another two AP2 genes ( DoAP2–2 and DoAP2–3 ) were up-related during flower development, which suggested that DoAP2 genes contribute to plant regeneration and flower development in Dendrobium officinale [ 18 ]. Overexpression of miR172, whose target is AP2 -like gene, resulted in the double flower phenotype in roses [ 19 ].…”

ERF5 enhances protocorm‐like body regeneration via enhancement of STM expression in Dendrobium orchid

“…BBM, encoding an AP2 domain protein, is a key regulator of somatic embryo development in monocot plants like rice and in dicot plants like Arabidopsis (Boutilier et al, 2002; Khanday et al, 2020). In our previous study, two genes (DoAP2-4 and DoAP2-13) annotated as BBM genes, did not preferentially express in PLBs in Dendrobium orchid (Zeng et al, 2021). The marker of somatic embryo development gene SERK is abundant in the zygotic embryos of sunflowers (Thomas et al, 2004).…”

“…The coding sequences of DoSTM and DoERF5 were cloned into the pSAT6–EYFP–N1 expression vector and fused in‐frame with YFP. The recombinant construct and plasmid of the nuclear localization marker (NLS–mCherry) were co‐transformed into Arabidopsis mesophyll protoplasts as previously described (Zeng et al, 2021). The primers used for subcellular localization analysis are listed in Table S1.…”

Orchid Biochemistry 2.0

“…Apetala 2 ( AP2 ) is a gene that codes for a transcription factor, and it belongs the AP2 / EREBP gene family, which plays key roles in regulating growth and development in plants. Zeng et al identified 14 homologs of AP2 in a popular medicinal orchid, Dendrobium officinale Kimura & Migo, namely DoAP2-1 to DoAP2-14 [ 5 ]. After subcellular localization and functional analysis of these genes, it was found that DoAP2 may encode transcriptional repressors and be involved in flower development, stress response and other biological activities.…”