Sibling competition and siblicide in asynchronously-hatching broods of the cattle egret Bubulcus ibis

Feeding behaviour and sibling competition were observed in nine families of the cattle egret (Bubulcus ibis) from blinds during 1359 nest-h throughout the nestling period. During days 0–19, size differences among siblings were clear; begging behaviour of chicks changed with time. At least one parent always attended the nest. Food boluses regurgitated early within a feeding period were received by senior chicks more often than by juniors. When any two siblings begged for food at the same time, the elder and younger received the first bolus on 65% and 35% of occasions respectively. Between days 20 and 39, the frequency of begging reached a peak. Begging behaviour became intense and stereotyped. The number of boluses received per begging declined rapidly, especially for junior chicks. In large broods, the success rate of begging was lower and fights occurred among siblings, especially among juniors. Out of 256 dyadic fights, the elder sibling won 85, lost one, and tied 171. The youngest chick died in two broods, apparently as the result of these fights (siblicide). No parents interfered in fights among their offspring. After day 40, the frequency of begging decreased gradually and ceased by day 80, No chicks died in the last period, although the frequency of fights in all large broods remained high.     

Seasonal aberrant radular formation in Thais bronni (Dunker) and T. clavigera (Küster) (Gastropoda : Muricidae)

Radulae of Thais bronni (Dunker) and T. clavigera (Küster) were examined at Mukaishima Island for a period of 2 yr, 1982 to 1984. Radulae of both species are similar in morphology, both having the basic pentacuspid rachidian plan. Sexual dimorphism of the radula was not observed, but rachidian tooth changes morphologically in different growth stages. Seasonal conditions affect the size and shape of the radula; in winter it is clearly malformed and strikingly thin. These aberrant parts of the radula comprised some dozens of rows, in which only several extremely thin rows exist. Results of experiments using T. clavigera under different water temperature conditions showed that the radula is rarely produced below 10 °C and that rate of radular production and replacement increases with increase in temperature. These results suggest that in the field the radula of these species is replaced entirely 2–2.5 times per year and 10–15 times during the life of the animal.     

Atg7 Activates an Autophagy-Essential Ubiquitin-like Protein Atg8 through Multi-Step Recognition

Atg8 is a unique ubiquitin-like protein that is covalently conjugated with a phosphatidylethanolamine through reactions similar to ubiquitination and plays essential roles in autophagy. Atg7 is the E1 enzyme for Atg8, and it activates the C-terminal Gly116 of Atg8 using ATP. Here, we report the crystal structure of Atg8 bound to the C-terminal domain of Atg7 in an unprecedented mode. Atg8 neither contacts with the central β-sheet nor binds to the catalytic site of Atg7, both of which were observed in previously reported Atg7–Atg8 structures. Instead, Atg8 binds to the C-terminal α-helix and crossover loop, thereby changing the autoinhibited conformation of the crossover loop observed in the free Atg7 structure into a short helix and a disordered loop. Mutational analyses suggested that this interaction mode is important for the activation reaction. We propose that Atg7 recognizes Atg8 through multiple steps, which would be necessary to induce a conformational change in Atg7 that is optimal for the activation reaction.     

Aminooxy‐naphthylpropionic acid and its derivatives are inhibitors of auxin biosynthesis targeting l‐tryptophan aminotransferase: structure–activity relationships

We previously reported l ‐α‐aminooxy‐phenylpropionic acid (AOPP) to be an inhibitor of auxin biosynthesis, but its precise molecular target was not identified. In this study we found that AOPP targets TRYPTOPHAN AMINOTRANSFERASE of ARABIDOPSIS 1 (TAA1). We then synthesized 14 novel compounds derived from AOPP to study the structure–activity relationships of TAA1 inhibitors in vitro. The aminooxy and carboxy groups of the compounds were essential for inhibition of TAA1 in vitro. Docking simulation analysis revealed that the inhibitory activity of the compounds was correlated with their binding energy with TAA1. These active compounds reduced the endogenous indole‐3‐acetic acid (IAA) content upon application to Arabidopsis seedlings. Among the compounds, we selected 2‐(aminooxy)‐3‐(naphthalen‐2‐yl)propanoic acid (KOK1169/AONP) and analyzed its activities in vitro and in vivo. Arabidopsis seedlings treated with KOK1169 showed typical auxin‐deficient phenotypes, which were reversed by exogenous IAA. In vitro and in vivo experiments indicated that KOK1169 is more specific for TAA1 than other enzymes, such as phenylalanine ammonia‐lyase. We further tested 41 novel compounds with aminooxy and carboxy groups to which we added protection groups to increase their calculated hydrophobicity. Most of these compounds decreased the endogenous auxin level to a greater degree than the original compounds, and resulted in a maximum reduction of about 90% in the endogenous IAA level in Arabidopsis seedlings. We conclude that the newly developed compounds constitute a class of inhibitors of TAA1. We designated them ‘pyruvamine’.     

The Arabidopsis dwf7/ste1 mutant is defective in the delta7 sterol C-5 desaturation step leading to brassinosteroid biosynthesis.

Lesions in brassinosteroid (BR) biosynthetic genes result in characteristic dwarf phenotypes in plants. Understanding the regulation of BR biosynthesis demands continued isolation and characterization of mutants corresponding to the genes involved in BR biosynthesis. Here, we present analysis of a novel BR biosynthetic locus, dwarf7 (dwf7). Feeding studies with BR biosynthetic intermediates and analysis of endogenous levels of BR and sterol biosynthetic intermediates indicate that the defective step in dwf7-1 resides before the production of 24-methylenecholesterol in the sterol biosynthetic pathway. Furthermore, results from feeding studies with 13C-labeled mevalonic acid and compactin show that the defective step is specifically the Delta7 sterol C-5 desaturation, suggesting that dwf7 is an allele of the previously cloned STEROL1 (STE1) gene. Sequencing of the STE1 locus in two dwf7 mutants revealed premature stop codons in the first (dwf7-2) and the third (dwf7-1) exons. Thus, the reduction of BRs in dwf7 is due to a shortage of substrate sterols and is the direct cause of the dwarf phenotype in dwf7.     

Occurrence of Potential Brassinosteroid Precursor Steroids in Seeds of Wheat and Foxtail Millet

Triticum aestivum L.) and foxtail millet (Setaria italica Beauv.) were found by GC-MS to contain, in addition to bulk sterols, 4-en-3-one steroids including 24-ethylcholesta-4,24(28)Z- dien-3-one (a new steroid), 24-methylcholest-4-en-3-one, 24-ethylcholesta-4,22E-dien-3-one and 24-ethylcholest-4-en-3-one, as well as 5α-steroidal 3-one compounds including 24-methyl-5α-cholestan-3-one, 24-ethyl-5α-cholestan-3-one and 24-ethyl 5α-cholest-22E-en-3-one (in S. italica only). Analysis of free sterol and steryl ester fractions indicated that campestanol and sitostanol were present at high levels in both seeds. These results suggest that the seeds of T. aestivum and S. italica synthesize campestanol from campesterol via 24-methylcholest-4-en-3-one and 24-methyl-5α-cholestan-3-one as has already been demonstrated in Arabidopsis thaliana L., and also produce sitostanol from sitosterol via 24-ethylcholest-4-en-3-one and 24-ethyl-5α-chotestan-3-one. Biosynthetic relationships of campestanol and sitostanol with C₂₈ and C₂₉ brassinosteroids are discussed. Received 4 September 1998/ Accepted in revised form 26 November 1998     

Human umbilical cord-derived cells can often serve as feeder cells to maintain primate embryonic stem cells in a state capable of producing hematopoietic cells

Clinical application of human embryonic stem (ES) cells will require the establishment of methods for their culture, either in the presence or absence of human-derived feeder cells. We have tested the ability of non-immortalized cultured cells derived from human umbilical cord (HUC cells) to support ES cell culture. A primate ES cell line that had been established and maintained with mouse embryonic fibroblasts was cultured on HUC cells for >3 months (HUC-maintained ES cells). These cells retained their expression of alkaline phosphatase, SSEA-4, Oct-3/4, and to a lesser extent Nanog, but did not express Rex-1. Nevertheless, HUC-maintained ES cells could produce ectoderm-, mesoderm- and endoderm-derived cells in teratomata that they formed in immunodeficient mice. We show that HUC-maintained ES cells could give rise to hematopoietic cells, although this ability of HUC cells varied among HUC cell populations derived from different neonates. HUC cells are promising as human material with which to maintain ES cells in a state that retains their ability to produce mature cells, including hematopoietic cells.