Flower development in Coffea arabica L.: new insights into MADS-box genes

Abstract

Coffea arabica L. shows peculiar characteristics during reproductive development, such as flowering asynchrony, periods of floral bud dormancy, mucilage secretion and epipetalous stamens. The MADS-box transcription factors are known to control several developmental processes in plants, including flower and fruit development. Significant differences are found among plant species regarding reproductive development and little is known about the role of MADS-box genes in Coffea reproductive development. Thus, we used anatomical and comparative molecular analyses to explore the flowering process in coffee. The main morphological changes during flower development in coffee were observed by optical and scanning electron microscopy. Flowering asynchrony seems to be related to two independent processes: the asynchronous development of distinct buds before the reproductive induction and the asynchronous development of floral meristems within each bud after the reproductive induction. A total of 23 C. arabica MADS-box genes were characterized by sequence comparison with putative Arabidopsis orthologs and their expression profiles were analyzed by RT-PCR in different tissues. The expression of the ABC model orthologs in Coffea during floral development was determined by in situ hybridization. The APETALA1 (AP1) ortholog is expressed only late in the perianth, which is also observed for the APETALA3 and TM6 orthologs. Conversely, the PISTILLATA ortholog is widely expressed in early stages, but restrict to stamens and carpels in later stages of flower development, while the expression of the AGAMOUS ortholog is always restricted to fertile organs. The AP1 and PISTILLATA orthologs are also expressed at specific floral organs, such as bracts and colleters, respectively, suggesting a potential role in the development of such structures. Altogether, the results from our comprehensive expression analyses showed significant differences between the spatiotemporal expression profiles of C. arabica MADS-box genes and their orthologs, which suggests differential functionalization in coffee. Moreover, these differences might also partially explain the particular characteristics of floral development in coffee, such as mucilage secretion and formation of epipetalous stamens.

How different is similar – exploring development of Ceropegia sandersonii pitfall flowers to elucidate convergent evolution of floral synorganization

“…E-class gene expression in Ceropegia was restricted to mature petals and gynostegia. This is different as compared with Aristolochia (26,42) and Erycina (33), where E-class gene expression was also found in early stage oral buds, but congruent with the nding for Coffea (43), where no E-class gene expression was detected in young oral buds either. The timing of E-class gene expression pattern found seems correlated with the positions of the species investigated in the Tree of Life for the Angiosperms (44): late stage E-class gene expression in Eudicots seems to have evolved from early and late stage expression in Monocots.…”

Ectopic expression ofJatropha curcas APETALA1(JcAP1) caused early flowering in Arabidopsis, but not in Jatropha

“…The JcAP1 coding sequence (CDS) (GenBank accession no. KR013222 ) is comprised of 732 bp and encodes a 243-amino acid protein showing 81%, 79%, 75%, and 71% sequence identity to Vitis vinifera VvAP1 ( Calonje et al, 2004 ), Populus trichocarpa PtAP1 ( Tuskan et al, 2006 ), Coffea arabica CaAP1 ( De Oliveira et al, 2014 ), and AtAP1 ( Mandel et al, 1992 ), respectively.…”

Homeologous regulation of Frigida-like genes provides insights on reproductive development and somatic embryogenesis in the allotetraploid Coffea arabica

“…arabica flowering mechanism had been provided by de Oliveira et al . 40 , indicating that, together with environmental cues, floral meristem ontogenesis is also an important factor that affects asynchronous flowering events. The same authors assessed MADS-box expression along floral development and discovered important differences between the spatiotemporal expression of classical Arabidopsis MADS-box and their orthologs in C .…”