DISPERSAL OF HETEROMORPHIC SEEDS IN AMPHICARPAEA BRACTEATA (FABACEAE)

The dispersal of the chasmogamous, aerial cleistogamous, and subterranean cleistogamous seeds of Amphicarpaea bracteata was examined. The chasmogamous and aerial cleistogamous seeds are ballistically dispersed. Chasmogamous seeds were dispersed farther than the aerial cleistogamous seeds due to the height advantage of the chasmogamous pods. There was no difference in the firing angle or the initial velocity of the seeds discharged from the two aerial pod types. The subterranean cleistogamous seeds are “dispersed” the shortest distance by the elongation of runners. Differential dispersal of the three types of seeds may be a factor involved in the evolution of cleistogamy in A. bracteata.     

Identification of low Ca2+ stress‐induced embryo apoptosis response genes in Arachis hypogaea by SSH‐associated library lift (SSHaLL)

Calcium is a universal signal in the regulation of wide aspects in biology, but few are known about the function of calcium in the control of early embryo development. Ca²⁺ deficiency in soil induces early embryo abortion in peanut, producing empty pods, which is a general problem; however, the underlying mechanism remains unclear. In this study, embryo abortion was characterized to be caused by apoptosis marked with cell wall degradation. Using a method of SSH cDNA libraries associated with library lift (SSHaLL), 62 differentially expressed genes were isolated from young peanut embryos. These genes were classified to be stress responses, catabolic process, carbohydrate and lipid metabolism, embryo morphogenesis, regulation, etc. The cell retardation with cell wall degradation was caused by up‐regulated cell wall hydrolases and down‐regulated cellular synthases genes. HsfA4a, which was characterized to be important to embryo development, was significantly down‐regulated under Ca²⁺‐deficient conditions from 15 days after pegging (DAP) to 30 DAP. Two AhCYP707A4 genes, encoding abscisic acid (ABA) 8′‐hydroxylases, key enzymes for ABA catabolism, were up‐regulated by 21‐fold under Ca²⁺‐deficient conditions upstream of HsfA4a, reducing the ABA level in early embryos. Over‐expression of AhCYP707A4 in Nicotiana benthamiana showed a phenotype of low ABA content with high numbers of aborted embryos, small pods and less seeds, which confirms that AhCYP707A4 is a key player in regulation of Ca²⁺ deficiency‐induced embryo abortion via ABA‐mediated apoptosis. The results elucidated the mechanism of low Ca²⁺‐induced embryo abortion and described the method for other fields of study.     

Genomic dissection of pod shattering in common bean: mutations at non‐orthologous loci at the basis of convergent phenotypic evolution under domestication of leguminous species

The complete or partial loss of shattering ability occurred independently during the domestication of several crops. Therefore, the study of this trait can provide an understanding of the link between phenotypic and molecular convergent evolution. The genetic dissection of ‘pod shattering’ in Phaseolus vulgaris is achieved here using a population of introgression lines and next‐generation sequencing techniques. The ‘occurrence’ of the indehiscent phenotype (indehiscent versus dehiscent) depends on a major locus on chromosome 5. Furthermore, at least two additional genes are associated with the ‘level’ of shattering (number of shattering pods per plant: low versus high) and the ‘mode’ of shattering (non‐twisting versus twisting pods), with all of these loci contributing to the phenotype by epistatic interactions. Comparative mapping indicates that the major gene identified on common bean chromosome 5 corresponds to one of the four quantitative trait loci for pod shattering in Vigna unguiculata. None of the loci identified comprised genes that are homologs of the known shattering genes in Glycine max. Therefore, although convergent domestication can be determined by mutations at orthologous loci, this was only partially true for P. vulgaris and V. unguiculata, which are two phylogenetically closely related crop species, and this was not the case for the more distant P. vulgaris and G. max. Conversely, comparative mapping suggests that the convergent evolution of the indehiscent phenotype arose through mutations in different genes from the same underlying gene networks that are involved in secondary cell‐wall biosynthesis and lignin deposition patterning at the pod level.     

Discovery of genomic regions and candidate genes controlling shelling percentage using QTL‐seq approach in cultivated peanut (Arachis hypogaea L.)

Cultivated peanut (Arachis hypogaea L.) is an important grain legume providing high‐quality cooking oil, rich proteins and other nutrients. Shelling percentage (SP) is the 2nd most important agronomic trait after pod yield and this trait significantly affects the economic value of peanut in the market. Deployment of diagnostic markers through genomics‐assisted breeding (GAB) can accelerate the process of developing improved varieties with enhanced SP. In this context, we deployed the QTL‐seq approach to identify genomic regions and candidate genes controlling SP in a recombinant inbred line population (Yuanza 9102 × Xuzhou 68‐4). Four libraries (two parents and two extreme bulks) were constructed and sequenced, generating 456.89–790.32 million reads and achieving 91.85%–93.18% genome coverage and 14.04–21.37 mean read depth. Comprehensive analysis of two sets of data (Yuanza 9102/two bulks and Xuzhou 68‐4/two bulks) using the QTL‐seq pipeline resulted in discovery of two overlapped genomic regions (2.75 Mb on A09 and 1.1 Mb on B02). Nine candidate genes affected by 10 SNPs with non‐synonymous effects or in UTRs were identified in these regions for SP. Cost‐effective KASP (Kompetitive Allele‐Specific PCR) markers were developed for one SNP from A09 and three SNPs from B02 chromosome. Genotyping of the mapping population with these newly developed KASP markers confirmed the major control and stable expressions of these genomic regions across five environments. The identified candidate genomic regions and genes for SP further provide opportunity for gene cloning and deployment of diagnostic markers in molecular breeding for achieving high SP in improved varieties.     

Proteomic Analysis of Differentially Expressed Proteins in Resistant Soybean Leaves after Phakopsora pachyrhizi Infection

Soybean rust caused by Phakopsora pachyrhizi is a destructive foliar disease in nearly all soybean‐producing countries. Understanding the host responses at the molecular level is certainly essential for effective control of the disease. To identify proteins involved in the resistance to soybean rust, differential proteomic analysis was conducted in soybean leaves of a resistant genotype after P. pachyrhizi infection. A total of 41 protein spots exhibiting a fold change >1.5 between the non‐inoculated and P. pachyrhizi‐inoculated soybean leaves at 12 and 24 h postinoculation (hpi) were unambiguously identified and functionally grouped into seven categories. Twenty proteins were up‐regulated and four proteins were down‐regulated at 12 hpi, whereas 18 proteins were up‐regulated and eight proteins were down‐regulated at 24 hpi. Generally, proteins involved in photosynthesis were down‐regulated, whereas proteins associated with disease and defense response, protein folding and assembly, carbohydrate metabolism and energy production were up‐regulated. Results are discussed in terms of the functional implications of the proteins identified, with special emphasis on their putative roles in defense. Abundance changes of these proteins, together with their putative functions reveal a comprehensive picture of the host response in rust‐resistant soybean leaves and provide a useful platform for better understanding of the molecular basis of soybean rust resistance.     

Carbon Exchange Rate of Intact Individual Soya Bean Pods. 1. Response to Step Changes in Light and Temperature

Carbon exchange rates (CER) of individual intact field-grownsoya bean [Glycine max (L.) Merr.] pods were measured continuouslywith a mobile gas analysis laboratory. Conditions in pod chamberssimulated those experienced normally by pods except for experimentalmodification of incident radiation or pod temperature. Undernormal conditions, CER (where positive CER represents CO₂ evolution)fluctuated diurnally with a morning rise followed by a slowafternoon and evening decline which was similar among pods whichwere measured simultaneously. The frequency of measurementspermitted detection of rapid CER responses to step changes inlight and pod temperature. CER rapidly decreased and increasedwhen the chamber was alternately exposed to full sunlight andcomplete darkness, respectively. CER responded similarly tosteps up [from ambient to elevated (+ 10°C) temperature]and steps down (from elevated to ambient temperature), respectively.Thus, a temperature sensitive process which regulated pod CERwas located within the pod. CER ranged from less than 0·1to more than 1·2 mg CO₂ h^–1 pod^–1 over theperiod of rapid dry-matter accumulation. Glycine max (L.) Merr., Soya bean, carbon exchange rate, light, temperature     

Identification of molecular markers for oocyte competence in bovine cumulus cells

Cumulus cells (CCs) have an important role during oocyte growth, competence acquisition, maturation, ovulation and fertilization. In an attempt to isolate potential biomarkers for bovine in vitro fertilization, we identified genes differentially expressed in bovine CCs from oocytes with different competence statuses, through microarray analysis. The model of follicle size, in which competent cumulus–oocyte complexes (COCs) were recovered from bigger follicles (≥8.0 mm in diameter) and less competent ones from smaller follicles (1–3 mm), was used. We identified 4178 genes that were differentially expressed (P < 0.05) in the two categories of CCs. The list was further enriched, through the use of a 2.5‐fold change in gene expression as a cutoff value, to include 143 up‐regulated and 80 down‐regulated genes in CCs of competent COCs compared to incompetent COCs. These genes were screened according to their cellular roles, most of which were related to cell cycle, DNA repair, energy metabolism, metabolism of amino acids, cell signaling, meiosis, ovulation and inflammation. Three candidate genes up‐regulated (FGF11, IGFBP4, SPRY1) and three down‐regulated (ARHGAP22, COL18A1 and GPC4) in CCs from COCs of big follicles (≥8.1 mm) were selected for qPCR analysis. The selected genes showed the same expression patterns by qPCR and microarray analysis. These genes may be potential genetic markers that predict oocyte competence in in vitro fertilization routines.