沙地生境和平茬年限对沙柳叶功能特征的影响

研究了毛乌素沙地南缘水滨边丘间地和干旱丘顶两种生境下沙柳平茬后不同年限(1、2、3～4和5～6年)对沙柳叶片光合气体交换、水分利用效率、结构特性及氮、磷养分含量等叶功能特征的影响.结果表明:水滨边丘间地沙柳叶片的净光合速率、气孔导度、瞬时和长期水分利用效率均高于丘顶,但N、P养分含量低于丘顶;两种生境下沙柳的叶结构性状无显著差异.干旱生境下沙柳主要通过增加养分含量、降低光合和水分利用来生存.随平茬年限增加,叶片净光合速率和气孔导度显著下降,氮含量和瞬时水分利用效率亦呈下降趋势,且二者之间呈显著正相关;平茬后1年的叶面积最高,比叶质量和叶干物质含量最低,此后比叶质量增加,叶面积和干物质含量不变;叶结构性状与光合及养分特性之间无显著相关性.叶光合活性和氮含量的下降是沙柳随平茬年限增加而衰败的重要原因.     

Trypanosoma cruzi: distinct patterns of infection in the sibling caviomorph rodent species Thrichomys apereoides laurentius and Thrichomys pachyurus (Rodentia, Echimyidae)

Thrichomys apereoides, a caviomorph rodent species common in a highly endemic area for Chagas disease in Brazil, may act as reservoir of the parasite. However, no information is available concerning its sibling species Thrichomys pachyurus, found in the Pantanal region, where Trypanosoma cruzi is found only in the enzootic cycle. We followed up the cross infection of these cryptic species with two isolates derived from naturally infected T. pachyurus and Thrichomys apereoides laurentius. No regional co-adaptation between Thrichomys species and the regional isolates were noticed. However, significant differences in the outcome of the infection were observed. T. a. laurentius was more resistant than T. pachyurus, as expressed by lower parasitemia and less histopathological damage. The routine biochemical markers used for laboratory rodents were unsuitable for follow up of infection in Thrichomys spp, since they did not correlate with the histopathological findings or allowed the kinetic follow-up of tissue colonization by the parasite.     

Mapping QTLs and candidate genes for iron and zinc concentrations in unpolished rice of Madhukar×Swarna RILs

Identifying QTLs/genes for iron and zinc in rice grains can help in biofortification programs. 168 F(7) RILs derived from Madhukar×Swarna were used to map QTLs for iron and zinc concentrations in unpolished rice grains. Iron ranged from 0.2 to 224ppm and zinc ranged from 0.4 to 104ppm. Genome wide mapping using 101 SSRs and 9 gene specific markers showed 5 QTLs on chromosomes 1, 3, 5, 7 and 12 significantly linked to iron, zinc or both. In all, 14 QTLs were identified for these two traits. QTLs for iron were co-located with QTLs for zinc on chromosomes 7 and 12. In all, ten candidate genes known for iron and zinc homeostasis underlie 12 of the 14 QTLs. Another 6 candidate genes were close to QTLs on chromosomes 3, 5 and 7. Thus the high priority candidate genes for high Fe and Zn in seeds are OsYSL1 and OsMTP1 for iron, OsARD2, OsIRT1, OsNAS1, OsNAS2 for zinc and OsNAS3, OsNRAMP1, Heavy metal ion transport and APRT for both iron and zinc together based on our genetic mapping studies as these genes strictly underlie QTLs. Several elite lines with high Fe, high Zn and both were identified.     

High levels of Paleolithic Y-chromosome lineages characterize Serbia

Whether present-day European genetic variation and its distribution patterns can be attributed primarily to the initial peopling of Europe by anatomically modern humans during the Paleolithic, or to latter Near Eastern Neolithic input is still the subject of debate. Southeastern Europe has been a crossroads for several cultures since Paleolithic times and the Balkans, specifically, would have been part of the route used by Neolithic farmers to enter Europe. Given its geographic location in the heart of the Balkan Peninsula at the intersection of Central and Southeastern Europe, Serbia represents a key geographical location that may provide insight to elucidate the interactions between indigenous Paleolithic people and agricultural colonists from the Fertile Crescent. In this study, we examine, for the first time, the Y-chromosome constitution of the general Serbian population. A total of 103 individuals were sampled and their DNA analyzed for 104 Y-chromosome bi-allelic markers and 17 associated STR loci. Our results indicate that approximately 58% of Serbian Y-chromosomes (I1-M253, I2a-P37.2 and R1a1a-M198) belong to lineages believed to be pre-Neolithic. On the other hand, the signature of putative Near Eastern Neolithic lineages, including E1b1b1a1-M78, G2a-P15, J1-M267, J2-M172 and R1b1a2-M269 accounts for 39% of the Y-chromosome. Haplogroup frequency distributions in Western and Eastern Europe reveal a spotted landscape of paleolithic Y chromosomes, undermining continental-wide generalizations. Furthermore, an examination of the distribution of Y-chromosome filiations in Europe indicates extreme levels of Paleolithic lineages in a region encompassing Serbia, Bosnia-Herzegovina and Croatia, possibly the result of Neolithic migrations encroaching on Paleolithic populations against the Adriatic Sea.     

Small inverted repeats drive mitochondrial genome evolution in Lake Baikal sponges

Demosponges, the largest and most diverse class in the phylum Porifera, possess mitochondrial DNA (mtDNA) markedly different from that in other animals. Although several studies investigated evolution of demosponge mtDNA among major lineages of the group, the changes within these groups remain largely unexplored. Recently we determined mitochondrial genomic sequence of the Lake Baikal sponge Lubomirskia baicalensis and described proliferation of small inverted repeats (hairpins) that occurred in it since the divergence between L. baicalensis and the most closely related cosmopolitan freshwater sponge Ephydatia muelleri. Here we report mitochondrial genomes of three additional species of Lake Baikal sponges: Swartschewskia papyracea, Rezinkovia echinata and Baikalospongia intermedia morpha profundalis (Demospongiae, Haplosclerida, Lubomirskiidae) and from a more distantly related freshwater sponge Corvomeyenia sp. (Demospongiae, Haplosclerida, Metaniidae). We use these additional sequences to explore mtDNA evolution in Baikalian sponges, paying particular attention to the variation in the rates of nucleotide substitutions and the distribution of hairpins, abundant in these genomes. We show that most of the changes in Lubomirskiidae mitochondrial genomes are due to insertion/deletion/duplication of these elements rather than single nucleotide substitutions. Thus inverted repeats can act as an important force in evolution of mitochondrial genome architecture and be a valuable marker for population- and species-level studies in this group. In addition, we infer (((Rezinkovia+Lubomirskia)+Swartschewskia)+Baikalospongia) phylogeny for the family Lubomirskiidae based on the analysis of mitochondrial coding sequences from freshwater sponges.     

The Art Collector

Abstract

The initiating point of this paper was an article in AEPR by Peter J. Smith in March/April 2003. At the end of the article, Peter J. Smith provides a short answer.