草莓果实MADS-box基因保守片段的克隆与序列分析

根据多种植物MADS-box基因保守区序列设计简并引物,应用PCR技术从草莓绿果中分高出33条MADS-box基因cDNA片段.序列分析表明,这些片段长度在137 - 146 bp之间,包含基因起始密码子.推导的氨基酸序列与已登录的草莓的MADS-box基因同源性超过87％.推导的氨基酸序列与已知的革莓和其他物种调控果实发育成熟的MADs-box基因以及拟南芥的MADS-box家族基因进行系统发育分析,可将这些基因片段分科归入拟南芥MADS-box基因不同亚家族中,证明草莓果实中存在各类MADS-box家族基因,克隆的部分片段可能参与调控果实发育和成熟软化的调节.     

Maternal sex effects and inbreeding depression under varied environmental conditions in gynodioecious Fragaria vesca subsp. bracteata

Background and Aims

Gynodioecy (coexistence of females and hermaphrodites) is a sexual system that occurs in numerous flowering plant lineages. Thus, understanding the features that affect its maintenance has wide importance. Models predict that females must have a seed fitness advantage over hermaphrodites, and this may be achieved via seed quality or quantity. Females in a population of Fragaria vesca subsp. bracteata, a long-lived gynodioecious perennial, do not demonstrate a seed quantity advantage, so this study explored whether females produced better quality seed via maternal sex effects or avoidance of inbreeding depression (IBD).

Methods

Families of selfed and outcrossed seed were created using hermaphrodite mothers and families of outcrossed seed were created using female mothers. The effects of these pollination treatments were assessed under benign conditions early in life and under varied conditions later in life. To test for an effect of maternal sex, fitness components and traits associated with acclimation to variable environments of progeny of outbred hermaphrodites and females were compared. To test for expression of IBD, fitness parameters between inbred and outbred progeny of hermaphrodites were compared.

Key Results

Offspring of females were more likely to germinate in benign conditions and survive in harsh resource environments than outbred progeny of hermaphrodites. IBD was low across most life stages, and both the effect of maternal sex on progeny quality and the expression of IBD depended on both maternal family and resource condition of the progeny.

Conclusions

The effect of maternal sex and IBD on progeny quality depended on resource conditions, maternal lineage and progeny life stage. In conjunction with known lack of differences in seed quantity, the quality advantages and IBD observed here are still unlikely to be sufficient for maintenance of gynodioecy under nuclear inheritance of male sterility.     

Structured diversity in octoploid strawberry cultivars: importance of the old European germplasm

Understanding genetic structure and diversity information is critical for genetic association studies. In the octoploid cultivated strawberry (Fragaria×ananassa), genetic analyses were focussed on diversity, whereas genetic structure has been poorly explored. This study investigated the genetic structure in a genetic resources collection representing a wide range of the octoploid strawberry cultivars released mainly by North America and western and southern Europe, at different breeding periods and with various pedigrees. The relationship between varieties was examined using 23 microsatellite (simple sequence repeat, SSR) markers. Eight SSR markers were diploid, useful for cultivar discrimination with polymorphic information content (PIC) values between 0.29 and 0.74. Bayesian analyses of genetic structure identified four subpopulations. Three of them, American and modern northern European cultivars (AMNECs), American and modern southern European cultivars (AMSECs) and old European cultivars (OECs), reflected the European breeding history of the cultivated octoploid strawberry. The fourth subpopulation, ‘Intermediate’ group cultivars (IGCs), comprised various origins including OECs that were introgressed with wild species such as Fragaria chiloensis or Fragaria moschata. The OEC group gathered cultivars dating before 1960s, forming the most homogenous and stable subpopulation. The unweighted pair group method with arithmetic mean (UPGMA) dendrogram based on modified Nei and Li distance confirmed the separation of the AMSEC, AMNEC and OEC groups. In addition, significant differences were observed among the four subpopulations (AMNEC, AMSEC, OEC, IGC), with high variability within groups and between AMSEC and IGC. Our work underlined that the structure within the studied collection was mainly explained by the pedigree and the year of release than the geographical origin of cultivars. In addition, the important loss of diversity observed in the modern European cultivars and a trend towards using mainly American cultivars for breeding programmes led to the progressive abandonment of old European germplasm, which was revealed as a relative distinct and rich group. This European material should be protected and maintained, because it represents a potential source of original traits for broadening the genetic base of cultivated strawberry. In addition, diploid markers we identified can be used without ambiguity in phylogenetic and diversity studies, because they are genome‐specific. This study is the first step for further association studies in strawberry.     

Genetic architecture of sexual dimorphism in a subdioecious plant with a proto-sex chromosome

The rise of sexual dimorphism is thought to coincide with the evolution of sex chromosomes. Yet because sex chromosomes in many species are ancient, we lack empirical evidence of the earliest stages of this transition. We use QTL analysis to examine the genetic architecture of sexual dimorphism in subdioecious octoploid Fragaria virginiana. We demonstrate that the region housing the male-function locus controls the majority of quantitative variation in proportion fruit set, confirming the existence of a proto-sex chromosome, and houses major QTL for eight additional sexually dimorphic traits, consistent with theory and data from animals and plants with more advanced sex chromosomes. We also detected autosomal QTL, demonstrating contributions to phenotypic variation in sexually dimorphic traits outside the sex-determining region. Moreover, for proportion seed set we found significant epistatic interactions between autosomal QTL and the male-function locus, indicating sex-limited QTL. We identified linked QTL reflecting trade-offs between male and female traits expected from theory and positive integration of male traits. These findings indicate the potential for the evolution of greater sexual dimorphism. Involvement of linkage groups homeologous to the proto-sex chromosome in these correlations reflects the polyploid origin of F. virginiana and raises the possibility that chromosomes in this homeologous group were predisposed to become the sex chromosome.     

Resistance to crown rot (Phytophthora cactorum) in strawberry cultivars and in offspring from crosses between cultivars differing in susceptibility to the disease

During a period of five years (1998‐2002), 26 strawberry cultivars and five selections were tested for resistance to crown rot. Cold stored plants inoculated with zoospores of Phytophthora cactorum were used in all experiments. The results showed that resistance to P. cactorum varies greatly between cultivars, and the most resistant ones were Senga Sengana, Induka, Melody, Glima and Bogota, while the most susceptible were Tamella, Inga, Evita and Jonsok. The results were compared to those obtained by other authors, and there were clear indications that the genetic background affects the degree of susceptibility to P. cactorum. Many of the most resistant cultivars descend from Senga Sengana (e.g. Bounty, Glima, Induka and Melody), and several of the most susceptible cultivars have common parentage (e.g. Inga, Tamella, Elsanta and Evita). In a resistance test of the progeny from two separate crosses between a resistant and a susceptible cultivar 61% and 65% of the offspring were intermediately to very susceptible, and 17% and 13% were resistant at the level of Senga Sengana. Hence, there is a high risk of losing offspring with high levels of resistance if selection for resistance to crown rot is not performed at an early stage in a breeding programme.     

The bacterial community associated with adult vine weevil (Otiorhynchus sulcatus) in UK populations growing on strawberry is dominated by Candidatus Nardonella

Otiorhynchus sulcatus (Fabricius) (Coleoptera: Curculionidae), commonly known as black vine weevil or simply vine weevil, is an important pest of soft fruit and ornamental crops. This species is endemic to temperate areas of Europe but has spread to many other areas over the last century, including North America and Australasia. The ability of vine weevils to adapt to such different environments is difficult to reconcile with the parthenogenetic reproduction strategy, which is likely to underpin a low genetic diversity. It is therefore tempting to hypothesize that weevil adaptation to different environments is mediated, at least partly, by the microbial communities inhabiting these insects. As a first step towards testing this hypothesis we characterized the composition of the bacterial microbiota in weevils from populations feeding on strawberry plants across four geographically separate locations in the UK. We performed 16S rRNA gene Illumina amplicon sequencing, generating 2 882 853 high‐quality reads. Ecological indices, namely Chao1 and Shannon, revealed that the populations used for this study harboured a low diversity and an uneven bacterial microbiota. Furthermore, β‐diversity analysis failed to identify a clear association between microbiota composition and location. Notably, a single operational taxonomic unit phylogenetically related to Candidatus Nardonella accounted for 81% of the total sequencing reads for all tested insects. Our results indicate that vine weevil bacterial microbiota resembles that of other insects as it has low diversity and it is dominated by few taxa. A prediction of this observation is that location per se may not be a determinant of the microbiota inhabiting weevil populations. Rather, other or additional selective pressures, such as the plant species used as a food source, ultimately shape the weevil bacterial microbiota. Our results will serve as a reference framework to investigate other or additional hypotheses aimed at elucidating vine weevil adaptation to its environment.     

草莓FaTT10基因的克隆与表达分析

以‘红颜’草莓为研究材料,本研究采用RT-PCR技术克隆得到FaTT10基因并对其进行生物信息学分析,采用q-PCR技术分析其时空特异性表达模式。结果表明,其开放阅读框为1 704 bp,编码567个氨基酸,蛋白质分子量为62.36 kD,理论等电点为6.69。亚细胞定位预测显示,此基因定位于细胞质膜。同源性及进化树构建结果表明,草莓FaTT10与其他植物漆酶类序列同源性较高。实时荧光定量PCR分析表明,FaTT10在草莓果实不同发育时期及组织器官间均存在表达特异性:在叶、花、匍匐茎、根、茎和果实中都有表达,在小绿果实中表达量最高,在叶中表达量最低;在果实各发育阶段,FaTT10在小绿期表达量最高,随着发育时期推进,表达量逐渐降低。     

森林草莓全基因组MADS-box转录因子基因的鉴定及凤梨草莓果实FaMADS1基因克隆

本文利用生物信息学方法对森林草莓（Fragaria vesca）基因组数据库中MADS-box基因的数量、结构类型、序列特征及染色体定位进行分析。结果表明,获得70个含SRF-TF结构域的森林草莓Fv MADS基因,DNA长度289~14 596 bp,编码66~1 437个氨基酸残基,有21个Fv MADS没有内含子,在7条染色体上呈不均匀分布;68个Fv MADS蛋白序列含有保守基序Motif 1,最佳匹配序列为＂RQVTFSKRRNGLLKKAYELSVLCDAEVALIIFSSRGKLYEF＂。另外,从栽培品种‘丰香’草莓果实中克隆了Fa MADS1基因,该基因属于MADS-box基因家族,c DNA全长1 167 bp,编码区750 bp,推导编码249个氨基酸,具有MADS结构域和K-box结构域。