Characterization of linear-oblong pyrenoids with cp-DNA along their sides in Nitzschia sigmoidea (Bacillariophyceae)

Abstract

SUMMARYIn the past 10 years Nitzschia sigmoidea (Nitzsch) W. Sm. has begun to occur in Japanese rivers in various areas. It is a common diatom in Europe but was previously absent in Japan. Each chloroplast of N. sigmoidea contains many unusual linear-oblong structures. The internal structure of the chloroplast in this species was observed using epifluorescence and electron microscopy with immunolocalization techniques. The linear-oblong structures in the chloroplasts could hardly be observed by conventional light microscopy of living cells, but were obvious in cells stained with propionocarmine. Transmission electron microscopy showed that the cross sections of this structure were lanceolate to fusiform with penetration by a single thylakoid. In cells stained with DAPI, chloroplast DNA was detected along both sides of the linear-oblong structures, and DNA fibrils were detected by electron microscopy. Immunofluorescence microscopy of sectioned cells and also immunoelectron microscopy revealed specific localization of Rubisco between these DNA-containing areas, which divided at the same time as the chloroplast. Our observations confirmed that the linear-oblong structures are pyrenoids. The diversity of localization patterns of chloroplast DNA in diatoms is discussed.

Carbon acquisition by diatoms

“…Furthermore, a few diatoms have no pyrenoids, and, when pyrenoids do occur, they do not always have thylakoids running through them. However, the 'membrane'(when present) around the pyrenoids could represent the ends of thylakoids (Drum 1963;Drum and Pancratz 1964;Schmid 2001;Mayama et al 2004).…”

A DETAILED DESCRIPTION OF A DANISH STRAIN OFNITZSCHIA SIGMOIDEA, THE TYPE SPECIES OFNITZSCHIA, PROVIDING A REFERENCE FOR FUTURE MORPHOLOGICAL AND PHYLOGENETIC STUDIES OF THE GENUS

“…In most diatoms, the chloroplast nucleoid is arranged in a ring along the margin of the chloroplast. This includes N. vermicularis, which is Downloaded by [University of Montana] at 17:11 05 April 2015 morphologically similar to N. sigmoidea (Mayama et al 2004). These authors found that the DNA in N. sigmoidea was only detected on both sides of the linear-oblong pyrenoids and regarded this as an autapomorphic character.…”

“…The cells have two chloroplasts on opposite sides of the central nucleus adjacent to the girdle sides, with the bent edges of the two chloroplasts more or less overlapping (Geitler 1937). The chloroplasts have numerous elongate-rhomboidal pyrenoids scattered throughout the chloroplast (Geitler 1937, Schmid 2003, Mayama et al 2004). According to Mayama (2004), each pyrenoid is penetrated by a single thylakoid.…”

“…The chloroplasts have numerous elongate-rhomboidal pyrenoids scattered throughout the chloroplast (Geitler 1937, Schmid 2003, Mayama et al 2004). According to Mayama (2004), each pyrenoid is penetrated by a single thylakoid. In most diatoms, the chloroplast nucleoid is arranged in a ring along the margin of the chloroplast.…”

“…Mann 1986a, Mayama et al 2004) and hence only a few features will be mentioned here. The cells have two chloroplasts on opposite sides of the central nucleus adjacent to the girdle sides, with the bent edges of the two chloroplasts more or less overlapping (Geitler 1937).…”