Endomembrane-biased dimerization of ABCG16 and ABCG25 transporters determines their substrate selectivity in ABA-regulated plant growth and stress responses

ATP-binding cassette(ABC)transporters are integral membrane proteins that have evolved diverse func-tions fulfilled via the transport of various substrates.In Arabidopsis,the G subfamily of ABC proteins is particularly abundant and participates in multiple signaling pathways during plant development and stress responses.In this study,we revealed that two Arabidopsis ABCG transporters,ABCG16 and ABCG25,engage in ABA-mediated stress responses and early plant growth through endomembrane-specific dimerization-coupled transport of ABA and ABA-glucosyl ester(ABA-GE),respectively.We first revealed that ABCG16 contributes to osmotic stress tolerance via ABA signaling.More specifically,ABCG16 induces cellular ABA efflux in both yeast and plant cells.Using FRET analysis,we showed that ABCG16 forms oblig-atory homodimers for ABA export activity and that the plasma membrane-resident ABCG16 homodimers specifically respond to ABA,undergoing notable conformational changes.Furthermore,we demonstrated that ABCG16 heterodimerizes with ABCG25 at the endoplasmic reticulum(ER)membrane and facilitates the ER entry of ABA-GE in both Arabidopsis and tobacco cells.The specific responsiveness of the ABCG16-ABCG25 heterodimer to ABA-GE and the superior growth of their double mutant support an inhib-itory role of these twoABCGs in early seedling establishment via regulation of ABA-GE translocation across the ER membrane.Our endomembrane-specific analysis of the FRET signals derived from the homo-or heterodimerized ABcG complexes allowed us to link endomembrane-biased dimerization to the transloca-tion of distinct substrates by ABcG transporters,providing a prototypic framework for understanding the omnipotence of ABcG transporters in plant development and stress responses.

Substrate Selectivity of Glycerol-3-phosphate Acyl Transferase in Rice

Substrate selectivity of glycerol-3-phosphate acyltransferase （EC 2. 3. 1. 15） of rice （Oryza sativa L.） was explored in a comparative study of acyltransferases from seven plant species. In vitro labeling of acyl carrier protein （ACP） with ^14C or 3H showed that acyltransferase from chill-sensitive plants, such as rice that uses either oleic （18：1） or palmitic acid （16：0） as acyl donor at comparable rates, displays lower selectivity than the enzyme from chill-resistant plants, such as spinach, which preferentially uses oleic acid （18：1） rather than palmitic acid （16：0） as an acyl donor. This may be a result of the size and character of the substrate-binding pocket of acyltransferase. Homology modeling and protein structure-based sequence alignment of acyltransferases revealed that proteins from either chill-sensitive or chill-tolerant plants shared a highly conserved domain containing the proposed substrate-binding pocket. However, the aligned residues surrounding the substrate-binding pocket are highly heterogeneous and may have an influence mainly on the size of the substrate binding pockets of acyltransferases. The substrate selectivity of acyltransferase of rice can be improved by enlarging the substrate-binding pocket using molecular biological methods.

Habitat use and space preferences of Eurasian Bullfinches(Pyrrhula pyrrhula)in northwestern Iberia throughout the year

Background:For all vertebrates in general,a concerted effort to move beyond single season research is vital to improve our understanding of species ecology.Knowledge of habitat use and selection by Eurasian Bullfinches(Pyrrhula pyrrhula)is limited with regard to the non-breeding season.To date,research on the habitat of the Iberian subspecies iberiae consists of very general descriptions.In relation to space use,only broad features are available for the entire distribution range of Eurasian Bullfinches,including Iberia.Methods:In this study,seasonal preferences regarding habitat and space in a population of Eurasian Bullfinches are examined for the first time in the Iberian Peninsula,through direct observation during a six-year period.The essential habitat components,substrate selection and perch height were assessed.Results:Hedgerows were the key essential habitat component for bullfinches during all seasons.Nevertheless,small poplar plantations became increasingly important from winter to summer-autumn.Bullfinches perched mostly in shrubs/trees throughout the year,but there were significant seasonal changes in substrate use,ground and herbs being of considerable importance during spring-summer.Throughout the year,over half of the records corresponded to feeding,reaching almost 90%in winter.Generally,bullfinches perched noticeably lower while feeding.Male bullfinches perched markedly higher than females,notably singing males in spring-summer.Juveniles perched at a height not much lower than that of males.In all seasons,males tended to feed at greater heights than females.Bullfinches of different ages and sexes were seen bathing in all seasons except winter.Conclusions:Hedgerow habitat in general appeared to be valuable for bullfinches throughout the year.In summer and autumn,they selected sites with an abundance of food and shade,as well as shelter,a much-needed requirement for fledglings and moulting individuals.There was usually a close link between the most used and most consumed plant species in each season.Males appeared to assume a more important role in vigilance,and often they accompanied dependent young in June and July.Bullfinch conservation strategies should consider seasonal demand for habitat and space.

Robust chromophore-integrated MOFs as highly visible-white-light active and tunable size-selective photocatalysts towards benzothiazoles

Visible-light heterogeneous photocatalyst with high activity and selectivity is crucial for the development of organic transformations, but remains a formidable challenge. Herein, a simple and effective strategy was developed to integrate tetrazine moiety, a visible light active unit, into robust metal-organic frameworks(2D MOF-1(M), M = Co, Mn, Zn, and 3D MOF-2(Co)). MOF-1 series are isomorphous 2D porous frameworks, and MOF-2(Co) displays 3D porous framework. Interestingly, benefiting from the oxidative active species of O_(2)·-, these MOFs all exhibit obviously highly enhanced photocatalytic activities toward the straightforward condensation of o-aminothiophenol and aromatic aldehydes at room temperature in Et OH under visible-white-light irradiation. Notably, compared to 3D MOF, the 2D layered MOF-1(Co) exhibited more excellent catalytic activity with a wide range of substrates possessing preeminent tolerance of steric hindrance. Most impressively, MOF-1(Co) can be recycled at least five times without significant loss of catalytic activity or crystallinity, exhibiting excellent stability and reusability. This study sheds light on the wide-ranging prospects of visible light active 2D MOFs as green photocatalysts for the preparation of fine chemicals.

Influence of physical and chemical factors during foraging and culture of the symbiont fungus in Atta sexdens rubropilosa （Hymenoptera： Formicidae）

The aim of this paper is to investigate the influence of physical and chemical factors on transport and use of substrate for Atta sexdens rubropilosa workers. Three types of rectangular fragments were used to study the physical influence factors： filter paper with paraffin, filter paper without paraffin and polyester film. To study the chemical factors, some fragments were impregnated with organic extract of orange albedo, others were soaked with soybean oil and for the remaining ones nothing was applied. The fonowing parameters were evaluated： （i） attractiveness of substrate for transport and number of loading workers per treatment; （ii） foraged material incorporation; （iii） rejection by numbers of fragments deposited in the garbage or beside the fungus garden. All the polyester film fragments carried out to the fungus garden were subsequently rejected. We verified that chemical factors of the substrate were more quickly detected by the workers, whereas physical factors were used as a criterion in the decision-making to reject or accept the substrate collected.