Genome-wide association study identified genetic variations and candidate genes for plant architecture component traits in Chinese upland cotton

Key message

Thirty significant associations between 22 SNPs and five plant architecture component traits in Chinese upland cotton were identified via GWAS. Four peak SNP loci located on chromosome D03 were simultaneously associated with more plant architecture component traits. A candidate gene, Gh_D03G0922, might be responsible for plant height in upland cotton.

Abstract

A compact plant architecture is increasingly required for mechanized harvesting processes in China. Therefore, cotton plant architecture is an important trait, and its components, such as plant height, fruit branch length and fruit branch angle, affect the suitability of a cultivar for mechanized harvesting. To determine the genetic basis of cotton plant architecture, a genome-wide association study (GWAS) was performed using a panel composed of 355 accessions and 93,250 single nucleotide polymorphisms (SNPs) identified using the specific-locus amplified fragment sequencing method. Thirty significant associations between 22 SNPs and five plant architecture component traits were identified via GWAS. Most importantly, four peak SNP loci located on chromosome D03 were simultaneously associated with more plant architecture component traits, and these SNPs were harbored in one linkage disequilibrium block. Furthermore, 21 candidate genes for plant architecture were predicted in a 0.95-Mb region including the four peak SNPs. One of these genes (Gh_D03G0922) was near the significant SNP D03_31584163 (8.40 kb), and its Arabidopsis homologs contain MADS-box domains that might be involved in plant growth and development. qRT-PCR showed that the expression of Gh_D03G0922 was upregulated in the apical buds and young leaves of the short and compact cotton varieties, and virus-induced gene silencing (VIGS) proved that the silenced plants exhibited increased PH. These results indicate that Gh_D03G0922 is likely the candidate gene for PH in cotton. The genetic variations and candidate genes identified in this study lay a foundation for cultivating moderately short and compact varieties in future Chinese cotton-breeding programs.

     

Duplication and adaptive evolution of the chalcone synthase genes of Dendranthema (Asteraceae)

Chalcone synthase (CHS) is a key enzyme in the biosynthesis of flavonoids, which are important for the pigmentation of flowers and act as attractants to the pollinators. Genes encoding CHS constitute a multigene family in which the copy number varies among plant species and functional divergence appears to have occurred repeatedly. Plants of the Dendranthema genus have white, yellow, and pink flowers, exhibiting considerable variation in flower color. In this article, 18 CHS genes from six Dendranthema species were sequenced. Two of them were found to be pseudogenes. The functional Dendranthema CHS genes formed three well-supported subfamilies: SF1, SF2, and SF3. The inferred phylogeny of the CHS genes of Dendranthema and Gerbera suggests that those genes originated as a result of duplications before divergence of these two genera, and the function of Dendranthema CHS genes have diverged in a similar fashion to the Gerbera CHS genes; i.e., the genes of SF1 and SF3 code for typical CHS enzymes expressed during different stages of development, whereas the genes of SF2 code for another enzyme that is different from CHS in substrate specificity and reaction. Relative rate tests revealed that the Dendranthema CHS genes significantly deviated from clocklike evolution at nonsynonymous sites. Maximum likelihood analysis showed that the nonsynonymous-synonymous (omega = d(N)/d(S)) rate ratio for the lineage ancestral to SF2 was much higher than for other lineages, with some sites having a ratio well above one. Positive selective pressure appears to have driven the divergence of SF2 from SF1 and SF3.     

Genetic Variants in Meiotic Program Initiation Pathway Genes Are Associated with Spermatogenic Impairment in a Han Chinese Population

Background

The meiotic program initiation pathway genes (CYP26B1, NANOS1 and STRA8) have been proposed to play key roles in spermatogenesis.

Objective

To elucidate the exact role of the genetic variants of the meiosis initiation genes in spermatogenesis, we genotyped the potential functional genetic variants of CYP26B1, NANOS1 and STRA8 genes, and evaluated their effects on spermatogenesis in our study population.

Design, Setting, and Participants

In this study, all subjects were volunteers from the affiliated hospitals of Nanjing Medical University between March 2004 and July 2009 (NJMU Infertile Study). Total 719 idiopathic infertile cases were recruited and divided into three groups according to WHO semen parameters: 201 azoospermia patients (no sperm in the ejaculate even after centrifugation), 155 oligozoospermia patients (sperm counts <20×10⁶/ml) and 363 infertility/normozoospermia subjects (sperm counts >20×10⁶/ml). The control group consisted of 383 subjects with normal semen parameters, all of which had fathered at least one child without assisted reproductive technologies.

Measurements

Eight single nucleotide polymorphisms (SNPs) in CYP26B1, NANOS1 and STRA8 genes were determined by TaqMan allelic discrimination assay in 719 idiopathic infertile men and 383 healthy controls.

Results and Limitations

The genetic variant rs10269148 of STRA8 gene showed higher risk of spermatogenic impairment in the groups of abnormospermia (including azoospermia subgroup and oligozoospermia subgroup) and azoospermia than the controls with odds ratios and 95% confidence intervals of 2.52 (1.29–4.94) and 2.92 (1.41–6.06), respectively (P = 0.006, 0.002 respective). Notably, larger sample size studies and in vivo or in vitro functional studies are needed to substantiate the biological roles of these variants.

Conclusions

Our results provided epidemiological evidence supporting the involvement of genetic polymorphisms of the meiotic program initiation genes in modifying the risk of azoospermia and oligozoospermia in a Han-Chinese population.     

Macroalgae and nutrients promote algal turf growth in the absence of herbivores

Coral Reefs - Closely cropped algal turfs are characteristic of healthy coral reefs, but unchecked growth can cause transitions into long sediment-laden turfs, which may be an alternative degraded...     

Novel Reassortant Highly Pathogenic H5N2 Avian Influenza Viruses in Poultry in China

There has been multiple evidence that domestic poultry may act as a vessel for the generation of novel influenza A viruses. In this study, we have analyzed the evolution and pathogenicity of 4 H5N2 avian influenza viruses isolated from apparently healthy poultry from H5N1 virus endemic areas in China. Phylogenetic analysis revealed that two of these viruses, A/duck/Eastern China/1111/2011 (DK/EC/1111/11) and A/goose/Eastern China/1112/2011 (GS/EC/1112/11) were derived from reassortment events in which clade 2.3.4 highly pathogenic avian influenza (HPAI) H5N1 viruses acquired novel neuraminidase and nonstructural protein genes. Another two isolates, A/chicken/Hebei/1102/2010 (CK/HB/1102/10) and A/duck/Hebei/0908/2009 (DK/HB/0908/09), possess hemagglutinin (HA) gene belong to clade 7 H5 viruses and other genes from endemic H9N2 viruses, or from viruses of various subtypes of the natural gene pool. All of these H5N2 isolates bear characteristic sequences of HPAI virus at the cleavage site of HA, and animal experiments indicated that all of these viruses but DK/HB/0908/09 is highly pathogenic to chickens. In particular, DK/EC/1111/11 and GS/EC/1112/11 are also highly pathogenic to ducks and moderately pathogenic to mice. All of these 4 viruses were able to replicate in domestic ducks and mice without prior adaptation. The emergence of these novel H5N2 viruses adds more evidence for the active evolution of H5 viruses in Asia. The maintenance of the highly pathogenic phenotype of some of these viruses even after reassortment with a new NA subtypes, their ability to replicate and transmit in domestic poultry, and the pathogenicity in the mammalian mouse model, highlight the potential threat posed by these viruses to both veterinary and public health.     

Evolutionary Patterns of Gene Families Generated in the Early Stage of Vertebrates

In this paper we have analyzed 49 vertebrate gene families that were generated in the early stage of vertebrates and/or shortly before the origin of vertebrates, each of which consists of three or four member genes. We have dated the first (T₁) and second (T₂) gene duplications of 26 gene families with 3 member genes. The means of T₁ (594 mya) and T₂ (488 mya) are largely consistent to a well-cited version of two-round (2R) genome duplication theory. Moreover, in most cases, the time interval between two successive gene duplications is large enough that the fate of duplicate genes generated by the first gene duplication was likely to be determined before the second one took place. However, the phylogenetic pattern of 23 gene families with 4 members is complicated; only 5 of them are predicted by 2R model, but 11 families require an additional gene (or genome) duplication. For the rest (7 families), at least one gene duplication event had occurred before the divergence between vertebrate and Drosophila, indicating a possible misleading of the 4:1 rule (member gene ratio between vertebrates and invertebrates). Our results show that Ohno's 2R conjecture is valid as a working hypothesis for providing a most parsimonious explanation. Although for some gene families, additional gene duplication is needed, the credibility of the third genome duplication (3R) remains to be investigated. Received: 13 December 1999 / Accepted: 7 April 2000     

Novel allocolchicinoids with an eight membered B-ring: design, synthesis and inhibition of tubulin assembly

Several B-ring variations of O-methyl androbiphenyline (8), newly accessible from (-)-(M,7S)-colchicine via photooxygenation and subsequent endoperoxide-transformation, were synthesized and evaluated for their inhibitory effects on tubulin assembly in vitro. The amino-allocolchicinoid (9), a key compound in this study, was transformed to the highly potent ketone 10 and by oxidation with H2O2/Na2WO4 to a mixture of syn/anti-oximes, like 11 and 12. These could easily be transformed to hitherto unknown allocolchicinoids 13 and 14 with an eight membered B-ring lactam obtained via a Beckmann rearrangement. Surprisingly both do not notably affect tubulin assembly, despite obvious structural similarities with active analogues of the thiocolchicine- and azasteganacin-series.