Genomics of cellulose biosynthesis in poplars

Abstract

Summary Genetic improvement of cellulose production in commercially important trees is one of the formidable goals of current forest biotechnology research. To achieve this goal, we must first decipher the enigmatic and complex process of cellulose biosynthesis in trees. The recent availability of rich genomic resources in poplars make Populus the first tree genus for which genetic augmentation of cellulose may soon become possible. Fortunately, because of the structural conservation of key cellulose biosynthesis genes between Arabidopsis and poplar genomes, the lessons learned from exploring the functions of Arabidopsis genes may be applied directly to poplars. However, regulation of these genes will most likely be distinct in these two‐model systems because of their inherent biological differences. This research review covers the current state of knowledge about the three major cellulose biosynthesis‐related gene families from poplar genomes: cellulose synthases, sucrose synthases and korrigan cellulases. Furthermore, we also suggest some future research directions that may have significant economical impacts on global forest product industries.

In vitro demonstration of interactions among zinc-binding domains of cellulose synthases in Arabidopsis and aspen

“…Similar to Arabidopsis secondary CesAs, ZnBDs of all three aspen homologous secondary CesAs were also able to interact with each other, and thus were able to form homo-and heterodimers ( Table 3). This agrees with the coordinate expression of three secondary CesAs that we observed in aspen [17,18]. There is also a general opinion that Y2H leads to too many false positives.…”

“…Using co-immunoprecipitation and bimolecular fluorescence complementation it has been proved that in primary wall, AtCesA1 and AtCesA3 were required for composing the complex and AtCesA6 was partially needed but redundant with AtCesA2 and AtCesA5 [14]. Similar suggestions of possible involvement of CesA trios in secondary wall formation have been reported in rice [15], barley [16], aspen [17,18], and Eucalyptus [19] although such involvement has been suggested only on the basis of coordinate expression of three CesAs in respective cell wall forming plant cells.…”

“…We have previously cloned and characterized aspen orthologs of the same three secondary CesA genes (PtrCesA1, 2 and 3) that are coordinately expressed during xylem development [17,18]. We also demonstrate here that ZnBDs from PtrCesA1, 2 and 3 also strongly interact with each other.…”

Structure, organization, and functions of cellulose synthase complexes in higher plants

“…(iv) Globular domain A and B: the globular domains A and B are highly conserved among CESAs (Pear et al, 1996;Wu et al, 2000;Joshi, 2003b;Joshi et al, 2004); (Joshi, 2003a,b;Joshi et al, 2004).…”

“…Protein sequence comparisons of higher plant CESAs reveal that all CESAs are grouped into six distinct clades which contain members associated with the primary or secondary cell wall ( Figure 6) (Holland et al, 2000;Vergara and Carpita, 2001;Joshi et al, 2004;Liang and Joshi, 2004;Samuga and Joshi, 2004b;Nairn and Haselkorn, 2005;Somerville, 2006). In fact, orthologs of AtCesA1, AtCesA3, and AtCesA6 appear to be required for the synthesis of cellulose deposited in the primary cell walls (Fagard et al, 2000;Scheible et al, 2001;Burn et al, 2002;Doblin et al, 2002).…”