Global Analysis of the Role of Autophagy in Cellular Metabolism and Energy Homeostasis in Arabidopsis Seedlings under Carbon Starvation

Germination and early seedling establishment are developmental stages in which plants face limited nutrient supply as their photosynthesis mechanism is not yet active. For this reason, the plant must mobilize the nutrient reserves provided by the mother plant in order to facilitate growth. Autophagy is a catabolic process enabling the bulk degradation of cellular constituents in the vacuole. The autophagy mechanism is conserved among eukaryotes, and homologs of many autophagy-related (ATG) genes have been found in Arabidopsis thaliana. T-DNA insertion mutants (atg mutants) of these genes display higher sensitivity to various stresses, particularly nutrient starvation. However, the direct impact of autophagy on cellular metabolism has not been well studied. In this work, we used etiolated Arabidopsis seedlings as a model system for carbon starvation. atg mutant seedlings display delayed growth in response to carbon starvation compared with wild-type seedlings. High-throughput metabolomic, lipidomic, and proteomic analyses were performed, as well as extensive flux analyses, in order to decipher the underlying causes of the phenotype. Significant differences between atg mutants and wild-type plants have been demonstrated, suggesting global effects of autophagy on central metabolism during carbon starvation as well as severe energy deprivation, resulting in a morphological phenotype.     

Yield quantitative trait loci from wild tomato are predominately expressed by the shoot

Plant yield is the integrated outcome of processes taking place above and below ground. To explore genetic, environmental and developmental aspects of fruit yield in tomato, we phenotyped an introgression line (IL) population derived from a cross between the cultivated tomato (Solanum lycopersicum) and a wild species (Solanum pennellii). Both homozygous and heterozygous ILs were grown in irrigated and non-irrigated fields and evaluated for six yield components. Thirteen lines displayed transgressive segregation that increased agronomic yield consistently over 2?years and defined at least 11 independent yield-improving QTL. To determine if these QTL were expressed in the shoots or the roots of the plants, we conducted field trials of reciprocally grafted ILs; out of 13 lines with an effect on yield, 10 QTL were active in the shoot and only IL8-3 showed a consistent root effect. To further examine this unusual case, we evaluated the metabolic profiles of fruits from both the homo- and heterozygous lines for IL8-3 and compared these to those obtained from the fruit of their equivalent genotypes in the root effect population. We observed that several of these metabolic QTL, like the yield QTL, were root determined; however, further studies will be required to delineate the exact mechanism mediating this effect in this specific line. The results presented here suggest that genetic variation for root traits, in comparison to that present in the shoot, represents only a minor component in the determination of tomato fruit yield.     

Impaired binding of standard initiation factors mediates poliovirus translation attenuation

In the oral poliovirus vaccine, three attenuated virus strains generated by Albert Sabin are used. However, insufficient genetic stability of these strains causes major problems in poliovirus eradication. In infected cells, translation of the plus-strand poliovirus RNA genome is directed by the internal ribosome entry site (IRES), a cis-acting RNA element that facilitates the cap-independent binding of ribosomes to an internal site of the viral RNA. In each Sabin vaccine strain, a single point mutation in the IRES secondary-structure domain V is a major determinant of neurovirulence attenuation. Here we report how these decisive mutations in the IRES confer a reduction in poliovirus translation efficiency. These single-nucleotide exchanges impair the interaction of the standard translation initiation factor eIF4G with the IRES domain V. Moreover, binding of eIF4B and the polypyrimidine tract-binding protein and the association of ribosomes with the viral RNA are affected by these mutations. However, the negative effects of the IRES mutations are completely relieved by addition of purified eIF4F. This indicates that eIF4G is the crucial factor that initially binds to the poliovirus IRES and recruits the IRES to the other components of the translational apparatus, while impaired binding of eIF4G plays a key role in attenuation of poliovirus neurovirulence.     

Diversity of Fusarium Species Isolated from Weeds and Plant Debris in Croatia

Weeds are alternative hosts of plant pathogens and when colonized may not exhibit disease symptoms. In 2008 and 2009, samples of weeds and plant debris were collected from 12 locations in eastern Croatia, and 300 Fusarium isolates colonizing them were identified. Strains were grouped and identified based on morphology and amplified fragment length polymorphism (AFLP) patterns. Portions of the β‐tubulin and translocation elongation factor 1‐α genes were sequenced from representative strains of each group to confirm the identifications. Fourteen Fusarium species were identified with F. graminearum (20%), F. verticillioides (18%), F. oxysporum (16%), F. subglutinans (13%) and F. proliferatum (11%) all present as more than 10% of the population. Fusarium acuminatum, F. avenaceum, F. concolor, F. crookwellense (F. cerealis), F. equiseti, F. semitectum, F. solani, F. sporotrichioides and F. venenatum, were all present at frequencies < 8%. Our results indicate that economically important Fusarium spp. may be isolated from numerous alternative hosts during the off season and that weeds and plant debris can serve as a reservoir of genetically diverse inoculum.     

Differences in flavonoid constituents among the species ofFagonia sinaica complex (Zygophyllaceae)

Eight flavonol glycosides were detected in the three species of theFagonia sinaica complex. They were fully characterized as the 3-glucosides of kaempferol, quercetin and isorhamnetin, 3-rutinoside of quercetin and 3,7-diglucoside of quercetin and isorhamnetin. Two additional glycosides were partially characterized as a kaempferol 3,7-diglycoside and quercetin 3-diglycoside.     

Flavone glycosides of some Launaea species

Eight flavone glycosides were isolated from Launaea nudicaulis and identified as apigenin 7-glucoside and 7-gentiobioside, luteolin 7-glucoside, 7-     

Reactions of the adult female of the soft scale Kilifia acuminata to some physical factors in laboratory experiments (Homoptera: Coccoidea: Coccidae)

The soft scale insect, Kilifia acuminata (Signoret) reacts positively to light. The simple eyes are the photoreceptors by means of which the insect can sum up the light from various directions and steers in a path towards the high intensity beam. The insect reacts skototactically towards dark objects.
The linear velocity of the insect significantly increases with the increase of temperature. It has a zone of thermopreferendum extending between 22° and 32°C. Above 37°C, the insect is sensitive to small temperature differences of 2°C.
At different humidity combinations below 75% R.H., the insect prefers the moist side, while in the upper range above 83% R.H., it usually prefers the dry side. The preferred zone of humidity extends between 75 and 83%.
Orthokinesis, klinokinesis and klinotaxis are the main mechanisms regulating the insect reaction towards different physical factors.
The insect behaviour and its correlation to the normal environment is also discussed.     

Flavonoid races in lasthenia (Compositae)

Nine of the 13 taxa ofLasthenia in which two or more populations were examined for flavonoid constituents exhibited interpopulation variation in these constituents. In certain species entire classes of compounds were present in some races and absent from others. Some of these biochemical differences are due to the failure of certain steps to occur in the biosynthesis of various flavonoids from precursor compounds. Another pattern of variation involves intraspecific differences in the nature of flavonoid glycosides that are produced. In view of the close biosynthetic relationships among all the flavonoids produced byLasthenia, the genetic differences among the flavonoid races of a species may be small. Whether or not these biochemical differences have any adaptive significance is problematical at present.     

Effects of thyroid state alterations in ovo on the plasma levels of thyroid hormones and on the populations of fibers in the plantaris muscle of male and female chickens.

Propylthiouracil (PTU), thyroxine (T4) or thyreoliberin (TRH) were injected in ovo to modify the thyroid state of chicken embryos. Significant sexual differences were observed in the effects of these treatments on the plasma concentrations of thyroid hormones and on plantaris muscle characteristics (DNA, RNA, populations of muscle fibers) in 3- and 35-day old male and female chickens. The T4 plasma concentration is lower in control males; it is decreased in PTU treated females and in the T4 treated females at 35 days. The T3 plasma concentration is lowered at 3 days in all treated chickens and also at 35 days in the TRH treated animals. The slow (STnO) and the fast (FTOG) fibers of the plantaris are always more numerous in males. In controls, the number of FTOG fibers remains steady between 3 and 35 days; at the same time, the number of STnO fibers rises in males only. Both PTU and T4 treatments increase the number of the FTOG and the STnO fibers respectively before and after the 3rd day. TRH treatment increases the number of STnO fibers at 3 and 35 days in males, but reduces it at 3 days in females. Thus changes in the number of FTOG fibers can be induced during in ovo myogenesis, whereas the number of STnO fibers may increase after hatching.