Colleters in Bathysa nicholsonii K. Schum. (Rubiaceae): Ultrastructure, Secretion Protein Composition, and Antifungal Activity

Abstract

Colleters are secretory structures well distributed in many organs of Angiosperms. Ultrastructurally, the colleters secretory cell presents an enhanced endoplasmic reticulum, Golgi apparatus, and mitochondria. Secretion synthesis, transportation, and passage through outer cell wall is poorly characterized. This study characterized the anatomy and ultrastructure of BATHYSA NICHOLSONII (Rubiaceae) colleters and evaluated the presence of protein in the secretion and its antifungal property. Samples were collected and prepared according to usual techniques in light and electron microscopy, electrophoresis, and fungal growth inhibition assay. Colleters are of a standard type, cylindrical and elongated, formed by one secretory epidermal palisade layer, and a central axis formed by parenchymatic cells and a vascular trace. Epidermal cells have dense cytoplasm with abundant ribosome, a nucleus, enhanced endoplasmic reticulum and Golgi apparatus. The outer cell wall presented morphologically distinct layers. The presence of secretory cavities was noted in all outer cell wall extents. Secretion preparations analyzed by SDS-PAGE showed that B. NICHOLSONII secretion is a mixture of proteins with molecular masses covering a range of approximately 66 to 24 kDa. This preparation presented an inhibitory effect on the fungi spore growth.

Foliar colleters inMacrocarpaea obtusifolia(Gentianaceae): anatomy, ontogeny, and secretion

“…Future studies will be performed aiming to clarify the importance of the presence of proteins in the colleter secretion of Gentianaceae species from functional and phylogenetic perspectives. The proteins observed in the colleter secretion of M. obtusifolia may represent a character shared by families of the Gentianales, because they also occur in the colleter secretions of Apocynaceae (Dave et al 1987;Thomas et al 1989) and Rubiaceae (Thomas and Dave 1990;Klein et al 2004;de Castro Miguel et al 2006). However, absence of protein in the secretion is a common feature in colleters of the Myrtaceae, as reported by da Silva et al (2012) for 52 species belonging to 17 genera of the Myrtoideae.…”

“…On the other hand, mucilage can attract opportunistic organisms such as fungi and bacteria, causing damage to the meristems (Martins 2012); however, the proteins observed in the secretion of the colleters of M. obtusifolia could have antifungal activity, as pointed out by de Castro Miguel et al (2006) in B. nicholsonii (Rubiaceae), and be associated with defense mechanisms against microorganisms ( Klein et al 2004). Future studies will be performed aiming to clarify the importance of the presence of proteins in the colleter secretion of Gentianaceae species from functional and phylogenetic perspectives.…”

“…An additional role attributed to mucilage is to act as a substrate for bacterial growth, thus facilitating symbiotic interactions (Horner and Lersten 1968;Lersten 1974aLersten , 1974bLersten 1975;Lersten and Horner 1976). Klein et al (2004) suggested that the proteins in the colleter secretions of Simira (Rubiaceae) species are also associated with a defense function against microorganisms, and de Castro Miguel et al (2006) confirmed the antifungal activity of these proteins in Bathysa nicholsonii K. Schum. (Rubiaceae).…”

“…The secretion of colleters is mostly composed of mucilage (Fahn 1979;Thomas 1991;da Silva et al 2012) or a mixture of mucilage and terpenes and (or) resin (Fahn 1979;Subramanian et al 1989;Mangalan et al 1990;Barreiro and Machado 2007). However, other chemical compounds have been identified in the exudate as proteins in Apocynaceae (Dave et al 1987; Thomas et al 1989), Aquifoliaceae (González and Tarragó 2009), Orchidaceae (Mayer et al 2011), and Rubiaceae (Thomas and Dave 1990;Klein et al 2004;de Castro Miguel et al 2006); phenolic compounds in Apocynaceae (Martins 2012), and lipids in Apocynaceae (Appezzato-da-Glória and Estelita 2000), Fabaceae (Paiva 2009), Orchidaceae (Mayer et al 2011), and Rubiaceae (Machado et al 2012). Although the presence of various metabolites, in addition to mucilage, has been demonstrated in the colleter exudate of several species, no correlation between different chemical constitutions and taxonomic groups has been observed.…”

Estruturas secretoras em orgãos vegetativos de espécies de Barbatimão (<i>Dimorphandra mollis </i>Benth. e <i>Stryphnodendron adstringens </i>(Mart.) Coville - Leguminosae)

“…As muitas controvérsias a respeito dos coléteres devem ser geradas pela escassez de estudos, concentrados em poucas famílias, como Apocynaceae (Lersten, 1974;Thomas & Dave, 1989;Thomas et al, 1989;Thomas & Dave, 1991;Thomas & Dave, 1990a;Simões et al, 2006) e Rubiaceae (Miller et al, 1983;Thomas & Dave, 1990;Castro Miguel et al, 2006). Há poucos registros de coléteres para Aquifoliaceae (González & Tarragó, 2009) …”