Biomedical subjects

Daisuke Kitazawa

Publications and source records attributed to Daisuke Kitazawa.

5 recordsLinked to original sources

PubMed2005

Shoot circumnutation and winding movements require gravisensing cells.

Circumnutation and winding in plants are universal growth movements that allow plants to survive despite their sessile nature. However, the detailed molecular mechanisms controlling these phenomena remain unclear. We previously found that a gravitropic mutant of Japanese morning glory (Pharbitis nil or Ipomoea nil), Shidare-asagao (weeping), is defective not only in circumnutation but also in the winding response. This phenotype is similar to that of the Arabidopsis SCARECROW (SCR) mutant. We therefore investigated whether morning glory SCR (PnSCR) is involved in the weeping phenotype. We found that one amino acid was inserted into the highly conserved VHIID motif in weeping-type PnSCR; this mutation caused abnormal endodermal differentiation. We introduced either the mutant or WT PnSCR into Arabidopsis scr mutants for complementation tests. PnSCR of the WT, but not of weeping, rescued the shoot gravitropism and circumnutation of scr. These results show that both the abnormal gravitropism and the circumnutation defect in weeping are attributable to a loss of PnSCR function. Thus, our data show that gravisensing endodermal cells are indispensable for shoot circumnutation and the winding response and that PnSCR is responsible for the abnormal phenotypes of weeping.

Amino Acid Sequence↗

PubMed2005

Structure of the central hub of bacteriophage Mu baseplate determined by X-ray crystallography of gp44.

Bacteriophage Mu is a double-stranded DNA phage that consists of an icosahedral head, a contractile tail with baseplate and six tail fibers, similar to the well-studied T-even phages. The baseplate of bacteriophage Mu, which recognizes and attaches to a host cell during infection, consists of at least eight different proteins. The baseplate protein, gp44, is essential for bacteriophage Mu assembly and the generation of viable phages. To investigate the role of gp44 in baseplate assembly and infection, the crystal structure of gp44 was determined at 2.1A resolution by the multiple isomorphous replacement method. The overall structure of the gp44 trimer is similar to that of the T4 phage gp27 trimer, which forms the central hub of the T4 baseplate, although these proteins share very little primary sequence homology. Based on these data, we confirm that gp44 exists as a trimer exhibiting a hub-like structure with an inner diameter of 25A through which DNA can presumably pass during infection. The molecular surface of the gp44 trimer that abuts the host cell membrane is positively charged, and it is likely that Mu phage interacts with the membrane through electrostatic interactions mediated by gp44.

Amino Acid Sequence↗

PubMed2005

Expression and characterization of a baseplate protein for bacteriophage Mu, gp44.

The gene product of gene 44 of Mu phage (gp44) is an essential protein for baseplate assembly and has been designated as gpP, a traditional genetic assignment. The function of gp44 during the assembly or infection process is not known. In the present study, we purified the recombinant gp44 and characterized it by analytical ultracentrifugation and differential scanning microcalorimetry. The results indicate that gp44 forms a trimer comprising a complex consisting of the 42 kDa and 40 kDa subunits that had been cleaved in the C-terminal region. Thermodynamic analysis also suggested that the C-terminal region forms a flexible domain.

Bacteriophage mu↗

PubMed2004

Crystallization and preliminary X-ray analysis of gene product 44 from bacteriophage Mu.

Bacteriophage Mu baseplate protein gene product 44 (gp44) is an essential protein required for the assembly of viable phages. To investigate the roles of gp44 in baseplate assembly and infection, gp44 was crystallized at pH 6.0 in the presence of 20% 2-methyl-2,4-pentanediol. The crystals belong to space group R3, with unit-cell parameters a = b = 127.47, c = 63.97 A. The crystals diffract X-rays to at least 2.1 A resolution and are stable in the X-ray beam and are therefore appropriate for structure determination. Native data have been collected to 2.1 A resolution using a DIP6040 image-plate system at beamline BL44XU at the SPring-8 facility in Japan.

Bacteriophage mu↗

PubMed2003

Effect of gravity on apical dominance in Pharbitis nil.

When the upper part of main shoot of morning glory (Pharbitis nil) is gently bent down, lateral bud on the bending region is released from apical dominance and starts to elongate. But, clinorotating the bending shoots prevents the release of the lateral bud from apical dominance. These results suggest that gravity affects apical dominance in morning glory. Here we verified the gravity-regulated apical dominance by using a weeping morning glory defective in gravitropic response due to abnormal differentiation of endodermis. That is, bending main shoot of the weeping morning glory hardly caused the lateral bud to elongate. In addition, decapitation of apical bud released the lateral bud from apical dominance, and exogenous auxin applied to the cut surface of the decapitated stem was inhibitory to the outgrowth of the lateral bud in the wild type. However, the effect of auxin was much less in the weeping morning glory. Thus, apical dominance of the weeping morning glory was weaker and less influenced by gravity than that of the wild type, which could occur due to abnormal differentiation of endodermis required for graviperception.

Flowers↗