Overexpression of Poplar Cellulase Accelerates Growth and Disturbs the Closing Movements of Leaves in Sengon

Abstract

In this study, poplar (Populus alba) cellulase (PaPopCel1) was overexpressed in a tropical Leguminosae tree, sengon (Paraserianthes falcataria), by the Agrobacterium tumefaciens method. PaPopCel1 overexpression increased the length and width of stems with larger leaves, which showed a moderately higher density of green color than leaves of the wild type. The pairs of leaves on the transgenic plants closed more slowly during sunset than those on the wild-type plants. When main veins from each genotype were excised and placed on a paper towel, however, the leaves of the transgenic plants closed more rapidly than those of the wildtype plant. Based on carbohydrate analyses of cell walls, the leaves of the transgenic plants contained less wall-bound xyloglucan than those of the wild-type plants. In situ xyloglucan endotransglucosylase activity showed that the incorporation of whole xyloglucan, potentially for wall tightening, occurred in the parenchyma cells (motor cells) of the petiolule pulvinus attached to the main vein, although the transgenic plant incorporated less whole xyloglucan than the wild-type plant. These observations support the hypothesis that the paracrystalline sites of cellulose microfibrils are attacked by poplar cellulase, which loosens xyloglucan intercalation, resulting in an irreversible wall modification. This process could be the reason why the overexpression of poplar cellulase both promotes plant growth and disturbs the biological clock of the plant by altering the closing movements of the leaves of the plant.

A Revised Architecture of Primary Cell Walls Based on Biomechanical Changes Induced by Substrate-Specific Endoglucanases

“…Plant genomes encode glycosyl hydrolases from 34 other enzyme families, two of which (families 9 and 16) may have endo-b-1,4-glucanase activity (Lopez-Casado et al, 2008), but it is unclear whether any of them exert the biomechanical effects of Cel12A. The plant growth effects observed with ectopic expression of plant cellulases may be mediated by a similar mechanism or by some other route (Park et al, 2003;Shani et al, 2004;Hartati et al, 2008). Auxin treatments result in slow increases in wall plastic and elastic compliances (Cleland, 1984), so the cell wall changes caused by Cel12A might be similar to those that occur during long-term auxin-induced growth.…”

Plant cell wall reconstruction toward improved lignocellulosic production and processability

“…Moreover, expression of a poplar endoglucanase (PaPopCel1) in Arabidopsis led to increased cell elongation and subsequent plant growth [101]. A similar effect was observed upon PaPopCel1 overexpression in the leguminous tropical tree (Paraserianthes falcataria) [102].…”

“…For example, it was seen that overexpression of poplar cellulase PaPopCel1 in the leguminous tropical tree P. falcataria, disturbs the biological clock of the plant by altering the closing movements of the leaves [102]. Undesirable physiological consequences can be prevented by using specific promoters directed to act at the specific organ, section or at preferred development stages, which one would like to modify.…”

Expression and initial characterization of a Phosphoinositide-specific phospholipase C from Populus tomentosa

“…Poplars are used to produce a great deal of wood-based products including timber, pulp and paper (Hartati et al 2008). More recently, its function as renewable energy has also been highlighted (Djomo et al 2011).…”