Downregulation of the Petunia hybrida α-Expansin Gene PhEXP1 Reduces the Amount of Crystalline Cellulose in Cell Walls and Leads to Phenotypic Changes in Petal Limbs

Abstract

The expansins comprise a family of proteins that appear to be involved in the disruption of the noncovalent bonds between cellulose microfibrils and cross-linking glycans, thereby promoting wall creep. To understand better the expansion process in Petunia hybrida (petunia) flowers, we isolated a cDNA corresponding to the PhEXP1 a-expansin gene of P. hybrida. Evaluation of the tissue specificity and temporal expression pattern demonstrated that PhEXP1 is preferentially expressed in petal limbs during development. To determine the function of PhEXP1, we used a transgenic antisense approach, which was found to cause a decrease in petal limb size, a reduction in the epidermal cell area, and alterations in cell wall morphology and composition. The diminished cell wall thickness accompanied by a reduction in crystalline cellulose indicates that the activity of PhEXP1 is associated with cellulose metabolism. Our results suggest that expansins play a role in the assembly of the cell wall by affecting either cellulose synthesis or deposition.

Cell Division and Expansion in Petals during Flower Development and Opening in <i>Eustoma grandiflorum</i>

“…Numerous proteins and enzymes are required for cell expansion. Genes encoding expansin, which is involved in cell wall loosening, are expressed during flower opening of carnation (Harada et al, 2011), Mirabilis jalapa (Gookin et al, 2003), and Petunia hybrida (Zenoni et al, 2004), and xyloglucan endotransglycosylase/ hydrolase (XTH) activity is associated with the opening of sandersonia flowers (O'Donoghue et al, 2002). Recently, Ochiai et al (2013a) reported that the expression of expansin and XTH genes and their proteins increased during flower opening in Eustoma.…”

Cell Division and Expansion Growth during Rose Petal Development

“…Some enzymes, such as invertase and sucrose synthase, are involved in the accumulation of soluble carbohydrates. Expansin, which is involved in cell wall loosening, is expressed during flower opening of tomato (Brummel et al, 1999), Mirabilis jalapa (Gookin et al, 2003) and Petunia hybrida (Zenoni et al, 2004), and xyloglucan endotranglycosylase/hydrolase (XTH) activity is associated with the opening of sandersonia flowers (O'Donoghue et al, 2002). We are now investigating enzyme activity and the gene expression responsible for cell expansion associated with flower opening.…”

The use of FTIR spectroscopy to monitor modifications in plant cell wall architecture caused by cellulose biosynthesis inhibitors

“…6 The use of PCA in conjunction with FTIR spectroscopy has proved to be an important tool in the study of cell wall structure and composition heterogeneity in a species, 7,8 or among different species, 5,9-11 as well as in the identification and classification of mutants with altered cell wall compositions. 6,[12][13][14] This approach has been also very useful in the characterization of the modifications appearing in this kind of mutants [15][16][17][18][19][20] or in transgenic plants with altered cell walls 21 and in the modifications to cell wall composition induced by different biotic or abiotic stress factors.…”