Autotetraploid rice is a useful germplasm for polyploid rice breeding, however, low seed setting is the major barrier in commercial utilization of autotetraploid rice. Our research group has developed neo-tetraploid rice lines, which have the characteristics of high fertility and heterosis when crossed with autotetraploid rice. In the present study, re-sequencing and RNA-seq were employed to detect global DNA variations and differentially expressed genes (DEGs) during meiosis stage in three neo-tetraploid rice lines compared to their parents, respectively. Here, a total of 4109881 SNPs and 640592 InDels were detected in neo-tetraploid lines compared to the reference genome, and 1805 specific presence/absence variations (PAVs) were detected in three lines. Approximately 12% and 0.5% of the total SNPs and InDels identified in three lines were located in genic regions, respectively. A total of 28 genes, harboring at least one of the large-effect SNP and/or InDel which affect the integrity of the encoded protein, were identified in the three lines. Together, 324 specific mutation genes, including 52 meiosis-related genes and 8 epigenetics-related genes were detected in neo-tetraploid rice compared to their parents. Of these 324 genes, five meiosis-related and three epigenetics-related genes displayed differential expressions during meiosis stage. Notably, 498 specific transcripts, 48 differentially expressed transposons and 245 differentially expressed ncRNAs were also detected in neo-tetraploid rice. Our results suggested that genomic structural reprogramming, DNA variations and differential expressions of some important meiosis and epigenetics related genes might be associated with high fertility in neo-tetraploid rice.
Hongkong qumquat (Fortunella hindsii Swingle) is a wild citrus species native to China. In this study, we firstly reporteded its complete chloroplast genome using BGISEQ-500 sequencing. The chloroplast genome is 160,145 bp in size, containing a large single copy region (87,467 bp), a small single copy region (18,730 bp), and a pair of IR regions (26,974 bp). The chloroplast genome contains 112 unique genes, including 79 protein-coding genes, 29 tRNAs, and 4 rRNAs. Phylogenetic maximum-likelihood analysis indicated that F. hindsii is closely related to Citrus species. The complete chloroplast genome would be subsequently used for citrus species researches. ARTICLE HISTORY
Pummelo cultivars are usually difficult to identify morphologically, especially when fruits are unavailable. The problem was addressed in this study with the use of two methods: high resolution melting analysis of SNPs and sequencing of DNA segments. In the first method, a set of 25 SNPs with high polymorphic information content were selected from SNPs predicted by analyzing ESTs and sequenced DNA segments. High resolution melting analysis was then used to genotype 260 accessions including 55 from Myanmar, and 178 different genotypes were thus identified. A total of 99 cultivars were assigned to 86 different genotypes since the known somatic mutants were identical to their original genotypes at the analyzed SNP loci. The Myanmar samples were genotypically different from each other and from all other samples, indicating they were derived from sexual propagation. Statistical analysis showed that the set of SNPs was powerful enough for identifying at least 1000 pummelo genotypes, though the discrimination power varied in different pummelo groups and populations. In the second method, 12 genomic DNA segments of 24 representative pummelo accessions were sequenced. Analysis of the sequences revealed the existence of a high haplotype polymorphism in pummelo, and statistical analysis showed that the segments could be used as genetic barcodes that should be informative enough to allow reliable identification of 1200 pummelo cultivars. The high level of haplotype diversity and an apparent population structure shown by DNA segments and by SNP genotypes, respectively, were discussed in relation to the origin and domestication of the pummelo species.
In this study, we reported the complete chloroplast genome of Fortunella crassifolia Swingle using the HiSeq-4000 sequencing. The chloroplast genome size is 160,229 bp, which consists of a large singlecopy region (87,774 bp), a small single-copy region (18,721 bp), and a pair of IR regions (26,867 bp). The chloroplast genome contains 114 unique genes, including 80 protein-coding genes, 30 tRNAs, and 4 rRNAs. Phylogenetic maximum likelihood analysis showed that F. crassifolia was closest to Hongkong kumquat (F. hindsii). The complete chloroplast genome would be subsequently used for citrus species researches.
Banana (Musa acuminata) is one of the most popular and widely consumed fruit crops in the world. During late October to early November 2020, a banana finger-tip rot disease was observed in the banana (cultivar ‘Brazil’, AAA group) orchard of about 12 hectares located in Zhongcun, Zhangmu Town, Fumian District, Yulin City, Guangxi province, China. The disease incidence was about 0.5% at the surveyed field. Infected fingers and their tips were usually normal in the appearances and then turned to brown to black discoloration in the central fruit pulp adjacent to the fingertips (Fig. 1A). In severe infection, diseased fingers showed brown to black discoloration in both the central and the periphery fruit pulp, and along the longitudinal axis throughout the fruit (Fig. 1B-C). The symptomatic banana fingers were surface-disinfected with 1% sodium hypochlorite for 30 sec, 75% ethanol for 30 sec then rinsed three times with sterile distilled water. The flesh tissues were ground in a sterile mortar and soaked in 1 ml of sterile distilled water for 30 min. A 50 μl of tissue suspensions was streaked onto Luria-Bertani (LB) medium. Single colonies were picked and re-streaked onto new LB medium. The cultures were incubated at 37°C for 24 h. Two representative strains, GX and GX2, were obtained from symptomatic pulps and used in the following studies. To molecularly identify the bacterial species, we performed a polymerase chain reaction (PCR) using 16S rRNA and recA primers (Turner et al. 1999; Lee and Chan 2007) and amplified 1,442 bp and 1,019 bp sequences, respectively. The amplified sequences were deposited in GenBank under the accession numbers MZ267253 and MZ961355 for the 16S rRNA and MZ287336 and MZ983484 for the recA genes. BLASTn searches shared more than 99% similarity with the reference sequences of B. cepacia strains (MK680073.1 and KC261418.1 for 16S rRNA; AY598028.1 and KF812859.1 for recA). Phylogenetic trees were constructed using the 16 rRNA and recA sequences and showed that the representative strains, GX and GX2, strongly clustered with B. cepacia type strains (Fig. 2). To further determine the genomovars of strain GX, we used specific PCR primers to the B. cepacia epidemic strain marker (BCESM), type III secretion gene cluster (bcscV) and cable pilin subunit gene (cblA) (Lee and Chan 2007; Ansari et al. 2019). The presence of bcscV and BCESM were confirmed by PCR, while cblA was not observed in the strains GX and GX2, suggesting that the isolated strains belong to B. cepacia genomovar III and are slightly different from the Iranian and Taiwan strains of B. cepacia (Lee and Chan 2007; Ansari et al. 2019). Pathogenicity test was conducted on banana fingers (cultivar ‘Zhongjiao No.3’) at the immature and full ripe stages. A final suspensions of 106 CFU/ml, was injected into the banana fingers (100 μl per finger) through the center of the stigma (Lee and Chan 2007; Ansari et al. 2019). The fingers inoculated with sterile water were used as negative control. To maintain humidity, the treated fingertips were wrapped with Parafilm. For each treatment, ten independent replicates were conducted. At 10 days post-inoculation (dpi), the pulp of immature bananas exhibited reddish brown decaying tissue, which symptoms were similar to those observed in the field (Fig. 1D). Moreover, the pulp tissues of ripe bananas showed a dark brown discoloration in the tip at 5 dpi, whereas the controls remained symptomless (Fig. 1E). The same bacterium was re-isolated from diseased tissues and its identification confirmed by 16S rRNA, thus fulfilling the Koch’s postulates. This disease was first described in Honduras in Latin America, and then reported in Taiwan province of China, and Iran (Buddenhagen 1968; Lee et al. 2003; Ansari et al. 2019). To our knowledge, this is the first report of banana finger-tip rot caused by B. cepacia in the Guangxi province, China. It is necessary to determine the distribution of B. cepacia and to prevent its spread in Guangxi province of China.
Citrus hongheensis is a key protected wild plant endemic to the Honghe river region in southeastern Yunnan, China. In the present study, its chloroplast genome was successfully assembled and annotated based on the Illumina Hiseq-2500 whole genome re-sequencing data. The chloroplast genome is 160,275 bp in size. Its large single copy region, small single copy region and inverted repeat region is 87,886 bp, 18,387 bp and 27,001 bp, respectively. Totally, 114 unique genes, including 80 protein-coding genes, 30 tRNAs and 4 rRNAs, were identified from the C. hongheensis chloroplast genome. According to the phylogenetic analysis result, the relationship between the chloroplast genome of C. hongheensis and C. maxima was found to be the closest.
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