ABSTRACT. UDP-glucuronate decarboxylase (UDP-xylose synthase; UXS, EC 4.1.1.35) is an essential enzyme of the non-cellulosic polysaccharide biosynthetic pathway. In the present study, using transient expression of fluorescently labeled Gossypium hirsutum UXS (GhUXS3) protein in onion epidermal cells, we observed that this protein was distributed in the cytoplasm. The GhUXS3 cDNA of cotton was expressed in an antisense orientation in Arabidopsis thaliana by Agrobacterium tumefaciensmediated transformation. Homozygous plants showing down-regulation of UXS were analyzed with northern blots. Compared to the untransformed control, transgenic plant showed shorter roots, earlier blossom formation, and delayed senescence. Biochemical analysis indicated that levels of rhamnose, mannose, galactose, glucose, xylose, and cellulose were reduced in some of the down-regulated antisense plants. These results suggest that GhUXS3 regulates the conversion of non-cellulosic polysaccharides and modulates their composition in plant cell walls. We also discuss a possible cellular function for GhUXS in determining the quality of cotton fibers.

In situ electrical resistivity measurement of powdered CdTe has been performed under high pressure using a diamond anvil cell equipped with a microcircuit. With the pressure increasing from 2.7 to 3.8 GPa, a sharp decrease in resistivity of over three orders of magnitude is observed. This is due to the appearance of rock-salt CdTe. At about 6.5 GPa a resistivity inflexion appears which has not been reported before. It is caused by the obvious decrease of band gap in certain symmetry directions of the Brillouin zone of rock-salt CdTe. From 6.5 to 10 GPa, the descending trend of the resistivity turns gently. At about 10 GPa, a cusp corresponding to the transition to the Cmcm phase is distinguished. Between 10 and 38 GPa, three leap points have been detected at 15.5 GPa, 22.2 GPa and 30 GPa, which imply abundant electronic phase transitions of CdTe. Resistivity measurements were also performed in a wide temperature range from liquid nitrogen temperature (77 K) to 450 K. It is proved that rock-salt CdTe does not show a typical metallic transport character. In the pressure range of 6.0–7.0 GPa, CdTe has a band gap of about 445 meV. The relationship of lnρ to 1/T is also fitted linearly to yield the ionization energy of impurities at different pressures.