Germinating spore exudates from arbuscular mycorrhizal fungi: molecular and developmental responses in plants and their regulation by ethylene

Arbuscular mycorrhizal (AM) fungi stimulate root development and induce expression of mycorrhization-specific genes in both eudicots and monocots. Diffusible factors released by AM fungi have been shown to elicit similar responses in Medicago truncatula. Colonization of roots by AM fungi is inhibited by ethylene. We compared the effects of germinating spore exudates (GSE) from Glomus intraradices in monocots and in eudicots, their genetic control, and their regulation by ethylene. GSE modify root architecture and induce symbiotic gene expression in both monocots and eudicots. The genetic regulation of root architecture and gene expression was analyzed using M. truncatula and rice symbiotic mutants. These responses are dependent on the common symbiotic pathway as well as another uncharacterized pathway. Significant differences between monocots and eudicots were observed in the genetic control of plant responses to GSE. However, ethylene inhibits GSE-induced symbiotic gene expression and root development in both groups. Our results indicate that GSE signaling shares similarities and differences in monocots versus eudicots, that only a subset of AM signaling pathways has been co-opted in legumes for the establishment of root nodulation with rhizobia, and that regulation of these pathways by ethylene is a feature conserved across higher land plants.     

Conserved and diverse mechanisms in root development

The molecular basis of root formation and growth is being analyzed in more and more detail in the dicot model organism Arabidopsis. However, considerable progress has also been made in the molecular and genetic dissection of root system development in the monocot species rice and maize. This review will highlight some recent molecular data that allow for the comparison of cereal and Arabidopsis root development. Members of the COBRA, GRAS, and LOB domain gene families and a gene encoding a subunit of the exocyst complex are associated with root development. Analyses of these genes revealed some common and distinct molecular principles and functions in cereal versus Arabidopsis root formation.     

Sugar effects on early seedling development in Arabidopsis

Sugars affect a broad variety of processes, from growth and development to gene expression. Although it has already been shown that sugars act as signaling molecules, little is known about the mechanisms by which plants respond to them. Much progress has been made on understanding sugar sensing and signaling thanks to the analysis of mutants with abnormal sugar response. Some of the genetic strategies applied are based on the inhibitory effect of sugar on post-germinative development of Arabidopsis thaliana. High concentrations of exogenous sugars delay germination and arrest early growth, preventing seedlings from expanding cotyledons and developing true leaves and an extensive root system. The characterization of several Arabidopsis mutants identified for their altered sugar sensitivity has disclosed a network in which sugars and plant hormones cooperate to control seedling development. Remarkably, many mutations turned out to be novel alleles of hormone-related genes, mainly ABA and ethylene. The aspects described above, emphasizing the connections between sugar and plant hormones revealed by mutants derived in seedling-based screens, are reviewed in this paper.     

The neurobiological context of autism

Autistic disorder (AD) is a complex neuropsychiatric disorder of neurodevelopmental origin, where multiple genetic and environmental factors may interact, resulting in a clinical continuum. The genetic component is best described by a multilocus model that takes into account epistatic interactions between several susceptibility genes. In the past ten years enormous progress has been made in identifying chromosomal regions in linkage with AD, but moving from chromosomal regions to candidate genes has proven to be tremendously difficult. Neuroanatomical findings point to early dysgenetic events taking place in the cerebral cortex, cerebellum, and brainstem. At the cellular level, disease mechanisms may include altered cell migration, increased cell proliferation, decreased cell death, or altered synapse elimination. Neurochemical findings in AD point to involvement of multiple neurotransmitter systems. The serotoninergic system has been intensively investigated in AD, but other neurotransmitter systems (e.g., the GABAergic and the cholinergic system) are also coming under closer scrutiny. The role of environmental factors is still poorly characterized. It is not clear yet whether environmental factors act merely as precipitating agents, always requiring an underlying genetic liability, or whether they represent an essential component of a pathogenetic process where genetic liability alone does not lead to the full-blown autism phenotype. A third potential player in the pathogenesis of autism, in addition to genetic and environmental factors, is developmental variability due to “random” factors, e.g. small fluctuations of gene expression and complex, non-deterministic interactions between genes during brain development. These considerations suggest that a non-deterministic conceptual framework is highly appropriate for autism research.     

Sex determination in plants

Sex determination is an important developmental event in the life cycle of all sexually reproducing plants. Recent studies of sex determination in many plant species, from ferns to maize, have been fruitful in identifying the diversity of genetic and epigenetic factors that are involved in determining the sex of the flower or individual. In those species amenable to genetic analysis, significant progress has been made toward identifying mutations that affect sex expression. By studying the interactions among these genes, pictures of how sex-determining signals are perceived to activate or repress male- or female-specific genes are emerging.     

发根农杆菌Ri质粒rol基因研究进展及在林木改良上的应用

Ri质粒上携带的诱根基因的表达不仅能导致植物被感染部位形成大量的毛根,而且由毛根容易获得再生的转化植株,这些植株可表现出许多能稳定遗传的表型变异,在植物遗传改良中有着广阔的应用前景。20世纪80年代以来,国内外学者对发根农杆菌Ri质粒及其rol基因进行了广泛深入的研究。本文重点综述了农杆碱型发根农杆菌Ri质粒的结构与功能,rol基因的位点与特征,Ri质粒的转化与rol基因的表达对植物生长发育的影响及在林木遗传改良上应用等方面的研究现状,并讨论了Ri质粒rol基因在林木遗传改良应用上存在的问题与应用前景。     

遗传学教学中性别决定关键基因的阐述

有性生殖的出现是生物进化中的重大事件。性别作为生物的一种重要而又复杂的表型, 由基因和环境因素共同控制, 其中遗传因素即基因起到非常关键的作用。 然而, 并不是每个相关基因对于生物的性别都具有相同的作用, 性别决定关键基因对生物性别的决定和性别的分化具有重要作用, 因而研究和理解性别决定的关键基因具有重要意义。随着现代遗传学的发展, 目前关于生物性别决定方式以及性别决定关键基因的研究已取得了很大的进展。文章就生物的基因性别决定机制以及基因性别决定机制的研究策略进行了综述, 以期在遗传学教学中能更好地理解和阐述。     

Filamentous fungi as cell factories for heterologous protein production

Filamentous fungi have been used as sources of metabolites and enzymes for centuries. For about two decades, molecular genetic tools have enabled us to use these organisms to express extra copies of both endogenous and exogenous genes. This review of current practice reveals that molecular tools have enabled several new developments. But it has been process development that has driven the final breakthrough to achieving commercially relevant quantities of protein. Recent research into gene expression in filamentous fungi has explored their wealth of genetic diversity with a view to exploiting them as expression hosts and as a source of new genes. Inevitably, the progress in the 'genomics' technology will further develop high-throughput technologies for these organisms.     

植物多基因转化研究进展

通过转基因技术改良植物品质近几年已成为热点研究问题,基因工程不断发展,单基因转化技术已不能满足人们对植物改良的需要。更多的研究者投身于参与某个代谢途径的多个基因在植物体中共同表达的研究,通过多基因调控来获得更好的植物性状。基因的协调表达有四种研究思路,在此基础上多基因转化方法可概述为传统转化法、改进后的共转化法,及新兴的基因融合方法,综合分析每种方法在植物代谢调控中的优缺点与应用,并探讨多基因整合的不稳定及相互作用问题。     

植物磷营养高效的分子生物学研究进展

挖掘利用植物自身的磷高效营养遗传资源是农业可持续发展的关键.磷高效营养性状涉及根形态、根分泌物、膜与体内磷转运以及菌根等许多方面,表现为数量遗传性状及受多基因控制.近年来,许多高亲和磷转运子基因已被克隆,磷向地上部转运和磷吸收负反馈调节的控制基因也被发现,对于根系分泌有机酸和酸性磷酸酶的基因的控制也有了一定的了解,但目前对于根毛、排根、根构型以及菌根的营养学意义性状的分子生物学研究进展缓慢.     

植物磷营养高效的分子生物学研究进展

挖掘利用植物自身的磷高效营养遗传资源是农业可持续发展的关键。磷高效营养性状涉及根形态、根分泌物、膜与体内磷转运以及菌根等许多方面,表现为数量遗传性状及受多基因控制。近年来,许多高亲和磷转运子基因已被克隆, 磷向地上部转运和磷吸收负反馈调节的控制基因也被发现, 对于根系分泌有机酸和酸性磷酸酶的基因的控制也有了一定的了解, 但目前对于根毛、排根、根构型以及菌根的营养学意义性状的分子生物学研究进展缓慢。     

A molecular genetic perspective of reproductive development in grapevine

The grapevine reproductive cycle has a number of unique features. Inflorescences develop from lateral meristems (anlagen) in latent buds during spring and summer and enter a dormant state at a very immature stage before completing development and producing flowers and berries the following spring. Lateral meristems are unique structures derived from the shoot apical meristem and can either develop into an inflorescence or a tendril. How the grapevine plant controls these processes at the molecular level is not understood, but some progress has been made by isolating and studying the expression of flowering genes in wild-type and mutant grapevine plants. Interestingly, a number of flowering genes are also expressed during berry development. This paper reviews the current understanding of the genetic control of grapevine flowering and the impact of viticulture management treatments and environmental variables on yield. While the availability of the draft genome sequence of grapevine will greatly assist future molecular genetic studies, a number of issues are identified that need to be addressed--particularly rapid methods for confirming gene function and linking genes to biological processes and traits. Understanding the key interactions between environmental factors and genetic mechanisms controlling the induction and development of inflorescences, flowers, and berries is also an important area that requires increased emphasis, especially given the large seasonal fluctuations in yield experienced by the crop and the increasing concern about the effect of climate change on existing wine-producing regions.     

植物抗虫基因工程研究进展

植物抗虫基因工程为防治农业害虫提供了一条崭新途径。本文对植物抗虫基因工程近年来所取得的某些研究进展,包括目前已发现和利用的抗虫基因、提高抗虫基因在植物体内表达的方法以及防止或延缓害虫产生抗性的策略等方面进行了综合评述,并对植物抗虫基因工程中有待解决的问题和发展前提提出了自己的看法。     

植物抗虫基因工程研究进展

植物抗虫基因工程为防治农业害虫提供了一条崭新途径。本文对植物抗虫基因工程近年来所取得的某些研究进展,包括目前已发现和利用的抗虫基因、提高抗虫基因在植物体内表达的方法以及防止或延缓害虫产生抗性的策略等方面进行了综合评述,并对植物抗虫基因工程中有待解决的问题和发展前景提出了自己的看法。     

发根农杆菌Ri质粒rol基因研究进展及在林木改良上的应用

Ri质粒上携带的诱根基因的表达不仅能导致植物被感染部位形成大量的毛根,而且由毛根容易获得再生的转化植株,这些植株可表现出许多能稳定遗传的表型变异,在植物遗传改良中有着广阔的应用前景。20世纪80年代以来,国内外学者对发根农杆菌Ri质粒及其rol基因进行了广泛深入的研究。本文重点综述了农杆碱型发根农杆菌Ri质粒的结构与功能,rol基因的位点与特征,Ri质粒的转化与rol基因的表达对植物生长发育的影响及在林木遗传改良上应用等方面的研究现状,并讨论了Ri质粒rol基因在林木遗传改良应用上存在的问题与应用前景。