Xyloglucan for generating tensile stress to bend tree stem.

In response to environmental variation, angiosperm trees bend their stems by forming tension wood, which consists of a cellulose-rich G (gelatinous)-layer in the walls of fiber cells and generates abnormal tensile stress in the secondary xylem. We produced transgenic poplar plants overexpressing several endoglycanases to reduce each specific polysaccharide in the cell wall, as the secondary xylem consists of primary and secondary wall layers. When placed horizontally, the basal regions of stems of transgenic poplars overexpressing xyloglucanase alone could not bend upward due to low strain in the tension side of the xylem.

Requirement of negative residues, Asp 95 and Asp 105, in S2 on membrane integration of a voltage-dependent K+ channel, KAT1.

Voltage-dependent K+ channels consist of a voltage-sensing region and a pore-forming region. Here we have identified the negative residues of the second transmembrane segment in the plant voltage-dependent K+ channel, KAT1, which involves the function of voltage sensing. Point mutations at D95 and D105 but not D89 and D116 failed to complement the K+ uptake deficient properties of the mutant yeast.

Diurnal difference in the amount of immunogold-labeled glucomannans detected with field emission scanning electron microscopy at the innermost surface of developing secondary walls of differentiating conifer tracheids.

The differences between cell wall formation at night, when the tangential strain used as an index of the volumetric changes in differentiating cells is high, and in the day, when the tangential strain is low, were investigated in Cryptomeria japonica D. Don. Samples containing differentiating xylem were collected at 0500 hours and 1400 hours.

Glycine residues in potassium channel-like selectivity filters determine potassium selectivity in four-loop-per-subunit HKT transporters from plants.

Plant HKT proteins comprise a family of cation transporters together with prokaryotic KtrB, TrkH, and KdpA transporter subunits and fungal Trk proteins. These transporters contain four loop domains in one polypeptide with a proposed distant homology to K(+) channel selectivity filters. Functional expression in yeast and Xenopus oocytes revealed that wheat HKT1 mediates Na(+)-coupled K(+) transport.