种子特异启动子调控ipt基因表达对烟草种子发育的影响

细胞分裂素（cytokinin，CTK）是五大类植物激素之一，它参与了植物许多生理过程与代谢的调控，主要有促进细胞的分裂和扩大，诱导芽、根和叶绿体的分化，促进种子与果实的发育，解除顶端优势，延缓叶片衰老及增强植物胁迫抗性，调节叶绿体发育基因、营养代谢基因及其它功能基因的表达，调控营养物质的运输和分配等。其调节的植物生理过程也受到其他不同因素的影响。细胞分裂素也是参与植物信号途径间相互作用的一类重要激素。 早期有关细胞分裂素生理作用的研究是基于外源激素的施用来进行的。由于通过外源施用细胞分裂素，其在植物体内的吸收，转运及代谢过程的复杂性和未知性，使得实验研究的因果关系难以确定。随着分子生物学的发展和植物转基因技术的日趋成熟，采用基因工程的方法来研究和探讨细胞分裂素对植物生长发育的调节作用及作用机理是近年来研究的热点，同时也为应用植物激素进行遗传育种提供了广阔的前景。 近年来，越来越多的真核生物启动子的分离克隆，促进了细胞分裂素基因工程的发展。利用具有组织特异性、发育特异性的启动子调控ipt基因，可使ipt基因在植物的特定组织或某一发育阶段进行表达。从而可根据不同的研究目的调控植物转化体中细胞分裂素合成的部位、时间和表达水平。尽管应用一些组织特异启动子融合ipt基因进行了一些细胞分裂素有关生理作用的研究，但是，有关细胞分裂素在胚和种子发育过程中的细胞学方面的研究还很少。 为研究ipt基因在种子发育过程中的作用，我们用大豆种子特异启动子-lectin融合ipt基因转化烟草，获得再生烟草植株。从生理学和细胞学上分析了ipt基因在lectin启动子的控制下的基因表达对种子生长发育的影响。发现在转基因烟草中，lectin-ipt基因的表达促进了种子胚及胚乳的细胞分裂，促使种子胚的生长加快，种子胚的增大为物质的贮存提供了条件，使营养物质更多的向种子运输，主要是可溶性蛋白质含量增加。由此进一步提高了转基因烟草种子干重的增加，种子的萌发与幼苗生长的加快，幼苗鲜重增加。

Dog chromosome-specific paints reveal evolutionary inter- and intrachromosomal rearrangements in the American mink and human

Forty chromosome-specific paint probes of the domestic dog (Canis familiaris, 2n = 78) were used to delineate conserved segments on metaphase chromosomes of the American mink (Mustela vison, 2n = 30) by fluorescence in situ hybridisation. Half of the 38 canine autosomal probes each painted one pair of homologous segments in a diploid mink metaphase, whereas the other 19 dog probes each painted from two to five pairs of discrete segments. In total, 38 canine autosomal paints highlighted 71 pairs of conserved segments in the mink. These painting results allow us to establish a complete comparative chromosome map between the American mink and domestic dog. This map demonstrates that extensive chromosome rearrangements differentiate the karyotypes of the dog and American mink. The 38 dog autosomes could be reconstructed from the 14 autosomes of the American mink through at least 47 fissions, 25 chromosome fusions, and six inversions. Furthermore, comparison of the current dog/mink map with the published human/dog map discloses 23 cryptic intrachromosomal rearrangements in 10 regions of conserved synteny in the human and American mink genomes and thus further refined the human/mink comparative genome map. Copyright (C) 2000 S. Karger AG, Basel.

Recent origin of a hominoid-specific splice form of neuropsin, a gene involved in learning and memory

Neuropsin is a secreted-type serine protease involved in learning and memory. The type II splice form of neuropsin is abundantly expressed in the human brain but not in the mouse brain. We sequenced the type II-spliced region of neuropsin gene in humans and representative nonhuman primate species. Our comparative sequence analysis showed that only the hominoid species (humans and apes) have the intact open reading frame of the type II splice form, indicating that the type II neuropsin originated recently in the primate lineage about 18 MYA. Expression analysis using RT-PCR detected abundant expression of the type II form in the frontal lobe of the adult human brain, but no expression was detected in the brains of lesser apes and Old World monkeys, indicating that the type II form of neuropsin only became functional in recent time, and it might contribute to the progressive change of cognitive abilities during primate evolution.

Y-chromosome evidence of southern origin of the East Asian - Specific haplogroup O3-M122

The prehistoric peopling of East Asia by modern humans remains controversial with respect to early population migrations. Here, we present a systematic sampling and genetic screening of an East Asian-specific Y-chromosome haplogroup (O3-M122) in 2,332 individuals from diverse East Asian populations. Our results indicate that the O3-M122 lineage is dominant in East Asian populations, with an average frequency of 44.3%. The microsatellite data show that the O3-M122 haplotypes in southern East Asia are more diverse than those in northern East Asia, suggesting a southern origin of the O3-M122 mutation. It was estimated that the early northward migration of the O3-M122 lineages in East Asia occurred similar to 25,000-30,000 years ago, consistent with the fossil records of modern humans in East Asia.

Adaptive evolution of MRGX2, a human sensory neuron specific gene involved in nociception

MRGX2, a G-protein-coupled receptor, is specifically expressed in the sensory neurons of the human peripheral nervous system and involved in nociception. Here, we studied DNA polymorphism patterns and evolution of the MRGX2 gene in world-wide human populations and the representative nonhuman primate species. Our results demonstrated that MRGX2 had undergone adaptive changes in the path of human evolution, which were likely caused by Darwinian positive selection. The patterns of DNA sequence polymorphisms in human populations showed an excess of derived substitutions, which against the expectation of neutral evolution, implying that the adaptive evolution of MRGX2 in humans was a relatively recent event. The reconstructed secondary structure of the human MRGX2 revealed that three of the four human-specific amino acid substitutions were located in the extra-cellular domains. Such critical substitutions may alter the interactions between MRGX2 protein and its ligand, thus, potentially led to adaptive changes of the pain-perception-related nervous system during human evolution. (c) 2005 Elsevier B.V. All rights reserved.

Detecting lineage-specific adaptive evolution of brain-expressed genes in human using rhesus macaque as outgroup

Comparative genetic analysis between human and chimpanzee may detect genetic divergences responsible for human-specific characteristics. Previous studies have identified a series of genes that potentially underwent Darwinian positive selection during huma

The testis-specific apoptosis related gene TTL.6 underwent adaptive evolution in the lineage leading to humans

The TTL.6 gene is a member of the tubulin-tyrosine ligase (TTL) family involved in apoptosis and preferentially expressed in the testis. We sequenced the coding region and part of the introns of TTL.6 in world wide human populations and five representativ

A human-specific mutation leads to the origin of a novel splice form of neuropsin (KLK8), a gene involved in learning and memory

Neuropsin (kallikrein 8, ELKS) is a secreted-type serine protease preferentially expressed in the central nervous system and involved in learning and memory. Its splicing pattern is different in human and mouse, with the longer form (type II) only express

Molecular evolution of a primate-specific microRNA family

Lineage-specific microRNA (miRNA) families may contribute to developmental novelties during evolution. However, little is known about the origin and evolution of new miRNA families. We report evidence of an Alu-mediated rapid expansion of miRNA genes in a

Functional characterization of the human-specific (type II) form of kallikrein 8, a gene involved in learning and memory

Kallikrein 8 (KLK8) is a serine protease functioning in the central nervous system, and essential in many aspects of neuronal activities. Sequence comparison and gene expression analysis among diverse primate species identified a human-specific splice for