SUMMARYCellulose synthase-like (CSL) proteins of glycosyltransferase family 2 (GT2) are believed to be involved in the biosynthesis of cell-wall polymers. The CSL D sub-family (CSLD) is common to all plants, but the functions of CSLDs remain to be elucidated. We report here an in-depth characterization of a narrow leaf and dwarf1 (nd1) rice mutant that shows significant reduction in plant growth due to retarded cell division. Map-based cloning revealed that ND1 encodes OsCSLD4, one of five members of the CSLD sub-family in rice. OsCSLD4 is mainly expressed in tissues undergoing rapid growth. Expression of OsCSLD4 fluorescently tagged at the C-or Nterminus in rice protoplast cells or Nicotiana benthamiana leaves showed that the protein is located in the endoplasmic reticulum or Golgi vesicles. Golgi localization was verified using phenotype-rescued transgenic plants expressing OsCSLD4-GUS under the control of its own promoter. Two phenotype-altered tissues, culms and root tips, were used to investigate the specific wall defects. Immunological studies and monosaccharide compositional and glycosyl linkage analyses explored several wall compositional effects caused by disruption of OsCSLD4, including alterations in the structure of arabinoxylan and the content of cellulose and homogalacturonan, which are distinct in the monocot grass species Oryza sativa (rice). The inconsistent alterations in the two tissues and the observable structural defects in primary walls indicate that OsCSLD4 plays important roles in cell-wall formation and plant growth.

Centromeres are required for faithful segregation of chromosomes in cell division. It is not clear what kind of sequences act as functional centromeres and how centromere sequences are organized in Oryza punctata, a BB genome species. In this study, we found that the CentO centromeric satellites in O. punctata share high homology with the CentO satellites in O. sativa. The O. punctata centromeres are characterized by megabase tandem arrays that are flanked by centromere-specific retrotransposons.Immunostaining with an antibody specific to CENH3 indicates that the 165-bp CentO satellites are the major component for functional centromeres. Moreover, both strands of CentO satellites are highly methylated and transcribed and produce small interfering RNA, which may be important for the maintenance of centromeric heterochromatin and centromere function.

The pigment is an important character in plant development. In the present study, we characterized and fine mapped one inhibitor for brown furrows gene (ibf) in rice (Oryza sativa L.). In the ibf mutant, brown pigments specifically accumulate in the furrows of hulls as seeds mature and reach a maximum level in dry seeds. Genetic analysis showed that the mutant phenotype is controlled by one recessive nuclear gene, which was finally mapped in a 90-kb region on the long arm of chromosome 9. Polymerase chain reaction and Southern blotting analysis revealed that there was a 26 kb deletion in the 90-kb region in the mutant. Since all the open reading frames outside the gap in the delimited region had no detectable difference in DNA sequence with the wild-type, we postulated that the ibf locus should be located in the gap. Through gene annotation and reverse transcription-polymerase chain reaction (RT-PCR) analysis, we selected OsKF1 encoding a kelch repeat-containing F-box family protein as the candidate gene of ibf.In most species, the coloration of flowers and fruits is due to the accumulation of flavonoid pigments (Quattrocchio et al. 2006). Understanding of the role of flavonoids as the major red, blue, purple and brown pigments in plants has attracted considerable interest over the years (Winkel-Shirly 2001). Flavonoids are plant secondary metabolites derived from the phenylpropanoid pathway and play a number of roles such as response to pathogens, protection from UV radiate and germination of pollen tubes. The major forms, which are anthocyanins (red to purple pigments), flavonols (colorless to pale yellow pigments) and proanthocyanidins also known as condensed tannins (colorless pigments that brown with oxidation) vary in proportion and amount according to the plant species, the organs, the stage of development and growth conditions (Debeaujon et al. 2001;Devic et al. 1999).In Arabidopsis, the flavonoid pathway has been mainly characterized using mutants which showed altered seed color for its seeds being characterized brown color (Debeaujon et al. 2001). To date, more than 20 loci involved in the flavonoid pathway have been characterized and seventeen genes have been