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Abstract

Four closely related cDNA clones encoding laccase isoenzymes from xylem tissues of yellow-poplar (Ltlacc2.1-4) were identified and sequenced. The inferred yellow-poplar laccase gene products were highly related to one another (79-91% at the amino acid level) and showed significant similarity to other blue copper oxidases, especially with respect to the copper-binding domains. The encoded proteins had N-terminal signal sequences and 17-19 potential N-linked glycosylation sites. The mature proteins were predicted to have molecular masses of ca. 61 kDa (unglycosylated) and high isoelectric points (pI 9.3-9.5). The canonical copper ligands were conserved, with the exception of a Leu residue associated with the axial position of the Type-1 cupric ion. The residue at this position has been proposed to influence the redox potential of Type-1 cupric ions. Northern blot analysis revealed that the yellow-poplar laccase genes are differentially expressed in xylem tissues. The genes were verified as encoding active laccases by heterologous expression in tobacco cells and demonstration of laccase activity in extracts from transformed tobacco cell lines.

Copper Active Sites in Biology

“…770,771 Molecular weights have been reported in the range from ~60–130kDa, 772,773 whereas pI values vary from 7.0–9.6. Most plant laccases are secreted proteins, with a few exceptions predicted to be targeted to the mitochondria.…”

Comprehensive Analysis of Rice Laccase Gene (OsLAC) Family and Ectopic Expression of OsLAC10 Enhances Tolerance to Copper Stress in Arabidopsis

“…Many studies have been conducted on fungal laccase, whereas studies on laccases in higher plants are limited and have considered disease resistance and lignin biosynthesis. Laccase has been isolated and identified in Arabidopsis thaliana , rice, tobacco, ryegrass, cotton, boxwood, poplar, and sycamore maple [5,6,7,8,9,10,11]. The most detailed study of laccase was on the Rhus vernicifera laccase [12].…”

Genome-Wide Identification of Sorghum bicolor Laccases Reveals Potential Targets for Lignin Modification

“…Laccase is widely distributed in plants, bacteria, fungi, and insects, while plant laccase is clustered in a separate clade in phylogenetic tree (Wang J. H. et al, 2015). To date, laccases have been characterized in many plants, such as Anacardiaceae, Arabidopsis thaliana (McCaig et al, 2005; Turlapati et al, 2011), Brachypodium distachyon (Wang Y. et al, 2015), Brassica napus (Zhang K. et al, 2013), cotton ( Gossypium arboreum ) (Wang et al, 2004), loblolly pine ( Pinus taeda ) (Bao et al, 1993), maize ( Zea mays ) (Caparrós-Ruiz et al, 2006; Liang et al, 2006b), poplar ( Populus trichocarpa ) (Ranocha et al, 1999), rice ( Oryza Sativa ) (Cho et al, 2014), ryegrass ( Lolium perenne ) (Gavnholt et al, 2002), sugarcane ( Saccharum officenarum ) (Cesarino et al, 2013), sycamore maple ( Acer pseudoplatanus ) (LaFayette et al, 1995), tobacco ( Nicotiana tabacum ) (Kiefer-Meyer et al, 1996), and yellow poplar ( Liridendron tulipifera ) (LaFayette et al, 1999). Diverse temporal and spatial expression patterns have been previously reported for plant laccases.…”