An unexpectedly sophisticated, V-shaped spermatozoon in Demospongiae (Porifera): reproductive and evolutionary implications

The demosponge Crambe crambe shows a peculiar spermatogenesis, hard to be reconciled with the basal position of sponges in the animal phylogeny. Early spermatogenesis stages showed most of the simple features expected in sponges. However, spermiogenesis departed from the anticipated process. Spermatids lengthened remarkably, forming a deep cytoplasmic pit around the cilium insertion, with the proximal axoneme bending to produce a V-shaped spermatozoon surprisingly similar to that known in the phylum Phoronida. The cytology was unexpectedly complex, with a needle-like nucleus of helically condensed chromatin, a conical acrosome with a subacrosomal rod, and a mitochondrion connected to the basal body by striated rootlets. These findings establish that the spermatozoon of broad-casting demosponges occurs in two structural categories ('primitive' and 'modified' type). This dualistic condition must necessarily have pre-dated the evolutionary apparition of higher metazoans, if we are to keep regarding sponges as the most primitive animals. We hypothesize that internal fertilization in C. crambe – and incidentally other demosponges – may depart from the general model assumed for spermcasting sponges. The V-shape of this spermatozoon suggests a design to favour autonomous penetration through the dense mesohyl to reach the oocytes, rather than engulfment and transportation by carrier cells towards the oocyte.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 413–426.     

Blubber testosterone: A potential marker of male reproductive status in short-beaked common dolphins

A novel molecular technique was used to measure blubber testosterone (BT) in 114 male short-beaked common dolphins, Delphinus delphis , collected from incidental fishery bycatch and strandings. When these concentrations were compared across maturity states, the mean (± SEM) BT levels of mature D. delphis (14.3 ± 3.0 ng/g) were significantly higher than those of pubertal (2.5 ± 0.5 ng/g, P = 0.006) and immature animals (2.2 ± 0.3 ng/g, P < 0.0001). BT concentrations in mature males were significantly higher in summer months (53.9 ± 2.0 ng/g) than during the rest of the year (7.9 ± 0.69 ng/g, P < 0.0001), indicating reproductive seasonality. An analysis of BT in different anatomical locations showed that hormone concentrations were not homogenous throughout the body; the levels in the dorsal fin were significantly lower than in most other areas ( F = 5.39, P = 0.043). Conversely, we found no significant differences in BT concentration with respect to subepidermal depth ( F = 2.09, P = 0.146). Finally, testosterone levels in biopsies from 138 free-swimming male D. delphis , of unknown maturity state, sampled off California were found to be of concentrations similar to those from the fishery bycatch and stranding samples and revealed an analogous trend with respect to ordinal date.     

Uracil salvage is necessary for early Arabidopsis development

Uridine nucleotides can be formed by energy-consuming de novo synthesis or by the energy-saving recycling of nucleobases resulting from nucleotide catabolism. Uracil phosphoribosyltransferases (UPRTs; EC 2.4.2.9) are involved in the salvage of pyrimidines by catalyzing the formation of uridine monophosphate (UMP) from uracil and phosphoribosylpyrophosphate. To date, UPRTs are described as non-essential, energy-saving enzymes. In the present work, the six genes annotated as UPRTs in the Arabidopsis genome are examined through phylogenetic and functional complementation approaches and the available T-DNA insertion mutants are characterized. We show that a single nuclear gene encoding a protein targeted to plastids, UPP , is responsible for almost all UPRT activity in Arabidopsis. The inability to salvage uracil caused a light-dependent dramatic pale-green to albino phenotype, dwarfism and the inability to produce viable progeny in loss-of-function mutants. Plastid biogenesis and starch accumulation were affected in all analysed tissues, with the exception of stomata. Therefore we propose that uracil salvage is of major importance for plant development.     

BFA‐induced compartments from the Golgi apparatus and trans‐Golgi network/early endosome are distinct in plant cells

Brefeldin A (BFA) is a useful tool for studying protein trafficking and identifying organelles in the plant secretory and endocytic pathways. At low concentrations (5–10 μg ml^?1), BFA caused both the Golgi apparatus and trans‐Golgi network (TGN), an early endosome (EE) equivalent in plant cells, to form visible aggregates in transgenic tobacco BY‐2 cells. Here we show that these BFA‐induced aggregates from the Golgi apparatus and TGN are morphologically and functionally distinct in plant cells. Confocal immunofluorescent and immunogold electron microscope (EM) studies demonstrated that BFA‐induced Golgi‐ and TGN‐derived aggregates are physically distinct from each other. In addition, the internalized endosomal marker FM4‐64 co‐localized with the TGN‐derived aggregates but not with the Golgi aggregates. In the presence of the endocytosis inhibitor tyrphostin A23, which acts in a dose‐ and time‐dependent manner, SCAMP1 (secretory carrier membrane protein 1) and FM4‐64 are mostly excluded from the SYP61‐positive BFA‐induced TGN aggregates, indicating that homotypic fusion of the TGN rather than de novo endocytic trafficking is important for the formation of TGN/EE‐derived BFA‐induced aggregates. As the TGN also serves as an EE, continuously receiving materials from the plasma membrane, our data support the notion that the secretory Golgi organelle is distinct from the endocytic TGN/EE in terms of its response to BFA treatment in plant cells. Thus, the Golgi and TGN are probably functionally distinct organelles in plants.     

银杏苗期生理生化指标的变异和选择研究

对银杏家系间的苗期生理生化和生长指标进行测定,并对生理生化指标与生长指标的相关关系进行研究。结果初步表明家系间生理生化指标、生长指标差异显著;叶片硝酸还原酶(NR)活性和单株生物量、苗高达到了极显著正相关水平;多酚氧化酶活性与单株生物量、苗高的相关系数达到极显著负相关水平。可以初步确定硝酸还原酶、多酚氧化酶为银杏苗木早期选择指标。     

ycaCR基因在文昌鱼早期胚胎表达研究

文昌鱼作为现存的与脊椎动物最接近的无脊椎动物,一直被作为研究生物进化和胚胎发育的典型材料.利用整体原位杂交方法对从文昌鱼肠cDNA文库克隆到的ycaCR基因进行基因的胚胎表达模式研究,结果显示该基因在早期胚胎发育阶段没有表达,在2天幼虫的原始消化道表达,暗示ycaCR基因可能在原始消化道内发挥生物学作用.     

An efficient procedure for embryogenic callus induction and double haploid plant regeneration through anther culture of Thai aromatic rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L. subsp. <Emphasis Type="Italic">indica</Emphasis>)

Anther culture is a biotechnology technique that can be used for the production of pure lines. The aims of this investigation were to induce embryogenic callus from major and minor culms of Thai aromatic rice cultivars and to subsequently regenerate double-haploid green plantlets by the application of exogenous polyamines. Embryogenic callus derived from anther culture was successfully induced in varieties KDML105, Homjan (HJ), and Pathumthani 1 (PT1). Production of embryogenic callus from anthers collected from the major culms was greater than those collected from the minor culms, especially in cultivar HJ. Plantlet regeneration in the three rice cultivars was observed from embryogenic callus and was highest, at 12.1%, from variety HJ treated with 0.5 mM spermidine. Plantlet regeneration from anther-derived embryogenic callus was dependent on the plant genotype, the types of exogenous polyamines, and the interactions of these factors. The percentage of haploid plantlets regenerated in PT1, KDML105, and HJ were 68.1%, 70.7%, and 78.5%, respectively. Only haploid plantlets were treated with colchicine for double-haploid production. This investigation has increased the knowledge of both embryogenic callus induction and plantlet regeneration in aromatic rice and has lead to the development of a pure, double-haploid line for the use in rice breeding programs in Thailand.