Biology subjects

Knox, J. P.

Publications and source records attributed to Knox, J. P..

3 recordsLinked to original sources

bioRxiv2026

Suppression of Pectinase Genes Confers Stable Enhancement of Fruit Firmness through Modulation of Pectin Structure in Strawberry

Fruit softening is primarily determined by modifications in the cell wall architecture, which are mediated by the coordinated activity of cell wall-degrading enzymes. In strawberry (Fragaria x ananassa Duch.), transgenic suppression of the genes encoding the pectinases polygalacturonase (PG), {beta}-galactosidase ({beta}Gal), and rhamnogalacturonan lyase (RGLyase), reduced fruit softening. In this study, we evaluated the fruit firmness phenotype of selected transgenic lines across several harvest years, from 3 to 9 years depending on the line, and analyzed the cell wall composition of ripe fruits using a carbohydrate microarray. Multiple linear regression analysis revealed that fruit firmness was significantly affected by both genotype and harvest year, while fruit size and soluble solids content showed no significant contribution. All pectinase-silenced lines exhibited increased firmness relative to the wild type, with those lines with PG down-regulated showing the most significant effects, followed by B-Gal and RGLyase fruits. The firmer phenotype was maintained stably in all the transgenic lines during the different years analyzed. Carbohydrate microarray analyses of sequentially extracted cell wall fractions demonstrated that transgenic ripe fruits retained higher levels of low methyl-esterified homogalacturonan (HG) and rhamnogalacturonan I (RG-I) epitopes compared to wild-type ripe fruits, resembling the composition of white-stage control fruits. Principal component analysis of microarray data revealed a clear separation between wild-type ripe fruits and transgenic lines, with the latter clustering near the earlier developmental stages of wild-type fruits. Correlation analysis further revealed positive associations between increased firmness and the abundance of high-methylated HG pectic epitopes in the water fraction, recognized with JIM7, and low-methylated HG abundance in the rest of the fractions (JIM5, LM18, and LM19). Overall, these results suggest that suppressing pectinase genes alters pectin remodeling during ripening, resulting in the retention of structurally intact pectin domains and increased fruit firmness. These genes are therefore excellent candidates for the improvement of this key quality trait in strawberry.

plant biology↗

bioRxiv2021

Cell Wall Biochemistry Drives Pollen Tube Mechanics and Affects Growth Rate

Pollen tubes maintain cell wall integrity as they rapidly grow towards the ovule, yet need to rupture at a precise moment to release the sperm cells. This biomechanical balance is critical for fertilization and relies on the interplay between turgor pressure and cell wall rigidity. How cell wall composition affects its mechanical properties is, however, not well understood. In this study, we combine experimental and simulation techniques to determine key mechanical parameters using Arabidopsis cell wall mutants. We integrated cellular force microscopy with a Finite Element Method-based model to predict growth rates of different mutant pollen tubes. The Finite Element Method-based model allowed us to quantify the effects of cell wall mutations on the time-independent turgor pressure and cell wall elasticity, while cellular force microscopy enabled determination of time-dependent viscoelastic properties of the cell wall. This novel approach can be applied across biological systems and advances mechanical studies of cell and tissue morphogenesis.

systems biology↗

bioRxiv2021

A soil-binding polysaccharide complex released from root hairs functions in rhizosheath formation

To elucidate factors involved in rhizosheath formation, wild type (WT) barley (Hordeum vulgare L. cv. Pallas) and a root hairless mutant, bald root barley (brb), were investigated with a combination of physiological, biochemical and immunochemical assays. When grown in soil, WT barley roots bound [~]5-fold more soil than brb per unit root length. High molecular weight (HMW) polysaccharide exudates of brb roots had less soil-binding capacity than those of WT root exudates. Carbohydrate and glycan monoclonal antibody analyses of HMW polysaccharide exudates indicated differing glycan profiles. Relative to WT plants, root exudates of brb had reduced signals for arabinogalactan-protein (AGP), extensin and heteroxylan epitopes than brb. In contrast, the brb root exudate contained [~]25-fold more detectable xyloglucan epitope relative to WT. Epitope detection chromatography indicated that the increased detection of xyloglucan in brb exudates was due to enhanced abundance of a neutral polymer. Exudate preparations from brb had decreased amounts of an acidic form of xyloglucan associated with root-hair located glycoprotein and heteroxylan epitopes and with soil-binding properties. Therefore, in addition to physically structuring soil particles, root hairs facilitate rhizosheath formation by releasing a soil-binding polysaccharide complex. One sentence summaryThe root exudate of a root hairless mutant of barley, relative to wild type, has an altered pattern of polysaccharide epitopes and lesser amounts of an acidic soil-binding polysaccharide complex.

plant biology↗