Does correlation of cellulase gene expression and cellulolytic activity in the gut of termite suggest synergistic collaboration of cellulases? Gaku Tokuda a , Hirofumi Watanabe b, ⁎ , Nathan Lo c a Center of Molecular Biosciences (COMB), University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan b National Institute of Agrobiological Science, Owashi, Tsukuba, Ibaraki 305-8634, Japan c School of Biological Sciences, The University of Sydeny, Sydney, New South Wales 2006, Australia Received 7 May 2007; received in revised form 25 June 2007; accepted 28 June 2007 Received by I.B. Rogozin Abstract Termites play an important role in degradation of dead plant materials in nature. Over the last century, many researchers have investigated the mechanisms of their lignocellulose digesting system. A recent publication by Zhou et al. (Zhou, X., Smith, J.A., Oi, F.M., Koehler, P.G., Bennett, G.W., Scharf, M.E., 2007. Correlation of cellulase gene expression and cellulolytic activity throughout the gut of the termite Reticulitermes flavipes. Gene 395, 29–39) dealt with the cellulolytic system of the flagellate-harboring termite R. flavipes and suggested “the presence of a single unified cellulose digestion system” in the termite, as an alternative hypothesis of a “dual (i.e. endogenous and symbiotic) cellulose digesting system” proposed by Nakashima et al. (Nakashima, K., Watanabe, H., Saitoh, H., Tokuda, G., Azuma, J.-I., 2002. Dual cellulose-digesting system of the wood-feeding termite, Coptotermes formosanus Shiraki. Insect Biochem. Mol. Biol. 32, 777–784). Here we show that their results actually support a dual cellulose digesting system rather than “a single unified cellulose digestion system”. In addition, potential problems with their results are highlighted. © 2007 Elsevier B.V. All rights reserved. Keywords: Cellulose digestion; Reticulitermes; Symbiont; Synergism Termites play an important role in degradation of lignocel- lulose, which is the most abundant biomass in nature. Thus, the digestive mechanisms used by termites to efficiently hy- drolyse lignocellulosic substances have interested many research- ers, since the early studies of Cleveland (1923), who also demonstrated symbiotic flagellates in the hindgut of the termite Reticulitermes flavipes essential for the host viability (Cleveland, 1924). In this context, Zhou et al. (2007) performed interesting experiments showing a correlation of both endogenous and symbiotic cellulase gene expression and cellulolytic activity throughout the gut of the termite R. flavipes. The results were suggested to support “synergistic collaboration between endog- enous and symbiotic cellulases from at least two distinct cellu- lase families (i.e. endo- and exoglucanases)” (in Discussion), and “the presence of a single unified cellulose digestion system” (in Abstract). This differs from the previous hypothesis of a “dual cellulose digesting system”, proposing the presence of two independent endogenous and symbiotic cellulolytic systems in flagellate-harboring (so-called “lower”) termites (Nakashima et al., 2002). In this letter, we point out some potential flaws in the conclusions of Zhou et al. (2007), and show that the results actually support the “dual cellulose digesting system” hypothesis. 1. Correlation of expression and activity does not suggest synergistic collaboration of termite cellulases The claim that “the presence of a single unified cellulose digestion system” requiring “synergistic collaboration between endogenous and symbiotic cellulases” is not supported by the experimental results presented by Zhou et al. (2007), which showed no convincing evidence for the synergistic collaboration of cellulases. The enzymatic synergism among cellulases is Gene xx (2007) xxx – xxx + MODEL GENE-35954; No of Pages 4 www.elsevier.com/locate/gene Abbreviation: EG, endoglucanase; GHF, glycosyl hydrolase family; EST, expressed sequence tag. ⁎ Corresponding author. Tel./fax: +81 29 838 6108. E-mail address: hinabe@affrc.go.jp (H. Watanabe). 0378-1119/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.gene.2007.06.028 ARTICLE IN PRESS Please cite this article as: Tokuda, G. et al. Does correlation of cellulase gene expression and cellulolytic activity in the gut of termite suggest synergistic collaboration of cellulases? Gene (2007), doi:10.1016/j.gene.2007.06.028