Effects of pollen supply and quality on seed formation and maturation in Pinus densiflora

To understand the detailed mechanisms underlying variations in seed productivity per cone, it is important to examine simultaneously the effects of two pollination mode components (pollen supply and quality) on two seed production processes (seed formation and maturation). We conducted artificial pollination experiments with four pollination treatments (selfing, polycross, no-pollination and open-pollination treatments) in each of two vertical crown layers (upper and lower) for 19 Pinus densiflora ramets. We measured formed seeds as a proportion of ovules (P(Form)), and filled seeds as a proportion of formed seeds (P(Fill)) per cone in each treatment and layer, and inferred the relative influences of pollination mode and resource availability on seed productivity. In the no-pollination treatment, no seeds were formed in any cones of all five ramets. The Generalized Linear Model showed that there were no significant differences in P(Form) both between selfing and polycross treatments and upper and lower layers. The mean P(Fill) values in the selfing treatment were significantly lower than those in the polycross treatment in both layers. The mean P(Fill)s of the two layers did not differ significantly in the selfing treatment, but did in the open-pollination and polycross treatments. The results show that pollen supply affects mainly seed formation, whereas pollen quality affects mainly seed maturation. Resource availability also affects mainly seed maturation, if pollen quality is higher than a certain threshold.     

Molecular determinants that convert hormone sensitive lipase into gibberellin receptor

Gibberellins (GAs) are tetracyclic, diterpenoid plant hormones, essential for many developmental processes in higher plants. Plants perceive GA through a nuclear-localized GA receptor, GA INSENSITIVE DWARF1 (GID1). From sequence similarity, it is suggested that GID1 evolved from a hormone-sensitive lipase (HSL), and recent x-ray crystallography of the GA-GID1 complex has given insights into how GID1 recognizes GA. Analyses of the GA signaling pathway in several plant species further suggest that the GID1-mediated GA signaling pathway emerged in the vascular plant lineage and since then regulation of GA recognition specificity seems to have been fine tuned to strictly regulate the on-off GA signal.     

Rapid determination of amino acids in biological samples using a monolithic silica column

A high-performance liquid chromatography method in which fluorescence detection is used for the simultaneous determination of 21 amino acids is proposed. Amino acids were derivatized with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) and then separated on a monolithic silica column (MonoClad C18-HS, 150 mm × 3 mm i.d.). A mixture of 25 mM citrate buffer containing 25 mM sodium perchlorate (pH 5.5) and acetonitrile was used as the mobile phase. We found that the most significant factor in the separation was temperature, and a linear temperature gradient from 30 to 49°C was used to control the column temperature. The limits of detection and quantification for all amino acids ranged from 3.2 to 57.2 fmol and 10.8 to 191 fmol, respectively. The calibration curves for the NBD-amino acid had good linearity within the range of 40 fmol to 40 pmol when 6-aminocaproic acid was used as an internal standard. Using only conventional instruments, the 21 amino acids could be analyzed within 10 min. This method was found to be suitable for the quantification of the contents of amino acids in mouse plasma and adrenal gland samples.     

Role of interaction of mannan-binding protein with meprins at the initial step of complement activation in ischemia/reperfusion injury to mouse kidney

Ischemia/reperfusion (I/R) is an important cause of acute renal failure. Recent studies have shown that the complement system mediated by the mannan-binding protein (MBP), which is a C-type serum lectin recognizing mannose, fucose and N-acetylglucosamine residues, plays a critical role in the pathogenesis of ischemic acute renal failure. MBP causes complement activation through the MBP lectin pathway and a resulting complement component, C3b, is accumulated on the brush borders of kidney proximal tubules in a renal I/R-operated mouse kidney. However, the initial step of the complement activation has not been studied extensively. We previously identified both meprins α and β, highly glycosylated zinc metalloproteases, localized on kidney proximal tubules as endogenous MBP ligands. In the present study, we demonstrated that serum-type MBP (S-MBP) and C3b were co-localized with meprins on both the cortex and the medulla in the renal I/R-operated mouse kidney. S-MBP was indicated to interact with meprins in vivo in the I/R-operated mouse kidney and was shown to initiate the complement activation through the interaction with meprins in vitro. Taken together, the present study strongly suggested that the binding of S-MBP to meprins triggers the complement activation through the lectin pathway and may cause the acute renal failure due to I/R on kidney transplantation and hemorrhagic shock.     

The suppressive function of the rice DELLA protein SLR1 is dependent on its transcriptional activation activity

When the gibberellin (GA) receptor GIBBERELLIN INSENSITIVE DWARF 1 (GID1) binds to GA, GID1 interacts with DELLA proteins, repressors of GA signaling. This interaction inhibits the suppressive function of DELLA protein and thereby activates the GA response. However, how DELLA proteins exert their suppressive function and how GID1s inhibit suppressive function of DELLA proteins is unclear. By yeast one-hybrid experiments and transient expression of the N-terminal region of rice DELLA protein (SLR1) in rice callus, we established that the N-terminal DELLA/TVHYNP motif of SLR1 possesses transactivation activity. When SLR1 proteins with various deletions were over-expressed in rice, the severity of dwarfism correlated with the transactivation activity observed in yeast, indicating that SLR1 suppresses plant growth through transactivation activity. This activity was suppressed by the GA-dependent GID1-SLR1 interaction, which may explain why GA responses are induced in the presence of GA. The C-terminal GRAS domain of SLR1 also exhibits a suppressive function on plant growth, possibly by directly or indirectly interacting with the promoter region of target genes. Our results indicate that the N-terminal region of SLR1 has two roles in GA signaling: interaction with GID1 and transactivation activity.     

Identification of 8-amino-2,5,7-trihydroxynaphthalene-1,4-dione, a novel intermediate in the biosynthesis of Streptomyces meroterpenoids

Furaquinocin is a natural polyketide-isoprenoid hybrid (meroterpenoid) produced by Streptomyces sp. strain KO-3988. All of the fur genes required for furaquinocin biosynthesis have been cloned, and the heterologous production of furaquinocin has been demonstrated in Streptomyces albus. Here, we report the identification of 8-amino-2,5,7-trihydroxynaphthalene-1,4-dione (8-amino-flaviolin) produced by the S. albus heterologous expression of the three contiguous genes encoding type III polyketide synthase (Fur1), monooxygenase (Fur2), and aminotransferase (Fur3) in the furaquinocin biosynthetic gene cluster. An S. albus transformant (S. albus/pWHM-Fur2_del3) harboring the fur gene cluster and lacking the fur3 gene did not produce furaquinocin, whereas furaquinocin production was restored when 8-amino-flaviolin was added to the culture medium of S. albus/pWHM-Fur2_del3. These results demonstrate that Fur3 aminotransferase is essential for furaquinocin biosynthesis and that 8-amino-flaviolin is an early-stage intermediate in furaquinocin biosynthesis. We propose that the biosynthetic pathway generating 8-amino-flaviolin is the common route for the biosynthesis of Streptomyces meroterpenoids.