Maltose excretion by the symbiotic Chlorella of the heliozoan Acanthocystis turfacea

Abstract

Abstract. C/;/or(?//a sp. strain 3.83, a symbiotic (Vy/fw/Za isolated from the heliozoan /^(Y/^^/?^rv\s7As ^r/rvrfrv, excreted between 8% and 16% of assimilated ^C02 as maltose in the light (15000 lx), with a pH optimum around 4.8. This percentage increased when the illuminance was lowered (36% at 1 700 lx). Release of [*^C]maltose continued in darkness and could be inhibited by the uncoupler carbonyl cyanide /7-trifluoro-methoxyphenylhydrazone and by diethylstilbestrol. Net efflux of maltose was observed even at a concentration ratio of extracellular/intracellular maltose of 7.8. Exogenous [*^C]maltose (5 mM) was taken up by the cells with a rate <2% of that of simultaneous maltose release, indicating a practically unidirectional transport. It is concluded that maltose excretion is an active-transport process.

Genome sequences of Chlorella sorokiniana UTEX 1602 and Micractinium conductrix SAG 241.80: implications to maltose excretion by a green alga

“…The three most prominent sugars found in extracellular sugars produced by algae associated with H. viridis are maltose, glucose and glucose‐6‐phosphate (Kessler et al ., ), while sucrose is not generally associated with extracellular sugars obtained from symbiotic Chlorella (Matzke et al ., ). Glucose, maltose and glucose‐6‐phosphate are all transient species resulting from starch degradation that would accumulate in the chloroplast were it not for specific transporters that are known to shuttle these sugars into the cytoplasm (Streb and Zeeman, ).…”

“…The accumulation of maltose in symbiotic algae has been described in a number of species (Cernichiari et al ., ; Ziesenisz et al ., ; Mews and Smith, ; Matzke et al ., ; Kessler et al ., ; Brechignac and Schiller, ; Dorling et al ., ; Hoshina et al ., ; Shibata et al ., ). While the accumulation of maltose or glucose in the culture medium is well documented, a clear understanding or even a simple pathway for the production of maltose for the purpose of sustaining this pathway and the association between the algae and the host is still lacking, even following more than 100 years of research in this field (Hoshina et al ., ; Pröschold et al ., ).…”

“…This differential expression should then be evident in the studies pursued here, which included RNA‐Seq global transcriptional studies (including genes highlighted in Table ). This system would be unable to support active transport, which has been indicated in certain model symbiotic Chlorella associated with A. turfacea and S. fluviatilis (Fischer et al ., ; Matzke et al ., ), but it is possible that elevated levels of intracellular maltose are sufficient to drive transport out of the cell when a suitable transporter is present. Our analysis of the RNA‐Seq results obtained here did identify quite a few genes that were differentially expressed under the lower pH conditions (pH 5.7) found to induce maltose release (Figure ; Table ), but none of these genes was specifically attributed to a known sugar uniporter family.…”

“…The release of sugars to the extracellular space in certain strains of green algae isolated from symbiotic associations is well documented (Mews and Smith, ; Douglas and Smith, ; Matzke et al ., ; Kessler et al ., ; Brechignac and Schiller, ; Dorling et al ., ; Summerer et al ., ; Shibata et al ., ). Algae isolated from symbiotic associations are often maintained within perialgal vacuoles inside the host.…”

Biomineralization by photosynthetic organisms: Evidence of coevolution of the organisms and their environment?

“…For key to superscripts explaining life forms see Table 1 footnotes. (1949), Raven (1983), Smith & Douglas (1987), Matzke et al (1990), Setoguchi et al (1993), Caron et al (1995), van den Hoek et al (1995), Epstein (1999), Graham & Wilcox (2000), Raven (2001) For key to superscripts explaining life forms see Table 1 footnotes.…”