Genomewide analysis of <Emphasis Type="Italic">ABCB</Emphasis>s with a focus on <Emphasis Type="Italic">ABCB1</Emphasis> and <Emphasis Type="Italic">ABCB19</Emphasis> in <Emphasis Type="Italic">Malus domestica</Emphasis>

The B subfamily of ATP-binding cassette (ABC) proteins (ABCB) plays a vital role in auxin efflux. However, no systematic study has been done in apple. In this study, we performed genomewide identification and expression analyses of the ABCB family in Malus domestica for the first time. We identified a total of 25 apple ABCBs that were divided into three clusters based on the phylogenetic analysis. Most ABCBs within the same cluster demonstrated a similar exon–intron organization. Additionally, the digital expression profiles of ABCB genes shed light on their functional divergence. ABCB1 and ABCB19 are two well-studied auxin efflux carrier genes, and we found that their expression levels are higher in young shoots of M106 than in young shoots of M9. Since young shoots are the main source of auxin synthesis and auxin efflux involves in tree height control. This suggests that ABCB1 and ABCB19 may also take a part in the auxin efflux and tree height control in apple.     

Cryopreservation of <Emphasis Type="Italic">Citrus</Emphasis> anthers in the National Crop Genebank of China

Genebank conservation of pollen is valuable because it makes genetic resources immediately available for use in breeding programs. In the case of Citrus species, conserved anthers or pollen can be easily transported and used to develop new varieties with pathogen resistance and desirable quality and yield traits. The aim of this study was to develop and improve air-desiccation cryopreservation protocols for Citrus cavaleriei and Citrus maxima anthers in genebanks. In the current study, warming, rehydration, and in vitro germination conditions were optimized to achieve high levels of in vitro germination in Citrus pollen for ten cultivars after liquid nitrogen (LN) exposure. The optimal warming, rehydration, and in vitro germination medium formulations affected the germination levels after pollen cryopreservation, with species- and cultivar-dependent effects. The Citrus anthers were dehydrated to the moisture content of 5–14% before LN exposure and warmed at 25 (cryopreserved Citrus anthers with a moisture content of lower than 10%) or 37°C (a moisture content of 10% or higher), then rehydrated, and cultured on medium with 150-g L^?1 sucrose, 0.1-g L^?1 boric acid, 1.0-g L^?1 calcium nitrate, 0.1-g L^?1 potassium nitrate, 0.3-g L^?1 magnesium sulfate, and 10-g L^?1 agar. After 2 yr of storage, in vitro germination levels of Citrus pollen after cryopreservation were significantly higher (> 22% for all ten cultivars) than those of samples that were stored at 4°C (0%). In vitro germination levels of pollen from six of ten cultivars after cryopreservation remained relatively high after 2 yr of storage (38–93%). The highest viability of 93% was obtained for C. cavaleriei ‘2–3’. The methods identified in the current study could be used to cryopreserve C. cavaleriei and C. maxima anthers.     

QTL mapping of mandarin (<Emphasis Type="Italic">Citrus reticulata</Emphasis>) fruit characters using high-throughput SNP markers

Seedlessness, flavor, and color are top priorities for mandarin (Citrus reticulata Blanco) cultivar improvement. Given long juvenility, large tree size, and high breeding cost, marker-assisted selection (MAS) may be an expeditious and economical approach to these challenges. The objectives of this study were to construct high-density mandarin genetic maps and to identify single nucleotide polymorphism (SNP) markers associated with fruit quality traits. Two parental genetic maps were constructed from an F₁ population derived from ‘Fortune’ × ‘Murcott’, two mandarin cultivars with distinct fruit characters, using a 1536-SNP Illumina GoldenGate assay. The map for ‘Fortune’ (FOR) consisted of 189 SNPs spanning 681.07 cM and for ‘Murcott’ (MUR) consisted of 106 SNPs spanning 395.25 cM. Alignment of the SNP sequences to the Clementine (Citrus clementina) genome showed highly conserved synteny between the genetic maps and the genome. A total of 48 fruit quality quantitative trait loci (QTLs) were identified, and ten of them stable over two or more samplings were considered as major QTLs. A cluster of QTLs for flavedo color space values L, a, b, and a/b and juice color space values a and a/b were detected in a single genomic region on linkage group 4. Two carotenoid biosynthetic pathway genes, pds1 and ccd4, were found within this QTL interval. Several SNPs were potentially useful in MAS for these fruit characteristics. QTLs were validated in 13 citrus selections, which may be useful in further validation and tentative MAS in mandarin fruit quality improvement.     

Pistil abortion in Japanese apricot (<Emphasis Type="Italic">Prunus mume</Emphasis> Sieb. et Zucc.): isolation and functional analysis of <Emphasis Type="Italic">PmCCoAOMT</Emphasis> gene

The abnormal pistils widely occur in Japanese apricot (Prunus mume Sieb. et Zucc) and seriously affect the fruit production. In this study, a CCoAOMT homologue, PmCCoAOMT, was cloned in Japanese apricot and the bioinformatics software analyzed the structural characteristics. The PmCCoAOMT protein was detected to be located in the cell cytoplasm by onion transient expression experiment. Analysis of the real-time PCR data showed that PmCCoAOMT gene expressed in the prophase development of pistil and the expression level in ‘Daqiandi’ was higher than ‘Longyan.’ The expression level in ‘Longyan’ was higher than ‘Daqiandi’ in the late period development of pistil, and the expression level of perfect flower (perfect pistil) was higher than imperfect flower (pistil deformity and no pistil). Compared with the control, the over-expression of PmCCoAOMT transgenic tobacco lines showed bigger flowers, darker petals. The lignin monomer composition in transgenic tobacco lines was also measured, and the results showed that transgenic tobacco lines had a higher S (Syringyl)/G (Guaiacyl) ratio (22.3 %) than control lines (11.8 %). Also, the perfect flower buds contained more S/G ratio (92.62 %) than imperfect flower buds (83.55 %) in ‘Daqiandi.’ Our results indicated that the PmCCoAOMT gene might have function in lignin accumulation, which contributed to pistil development in Japanese apricot.     

Knockout of <Emphasis Type="Italic">OsACOS12</Emphasis> caused male sterility in rice

Pollen development in flowering plants is critical for male reproductive success. The pollen wall that protects the pollen from various environment stresses and bacterial infections plays an essential role in pollen development. The formation of pollen wall is associated with the biosynthesis and transport of sporopollenin components. ACOS5 in Arabidopsis encodes an acyl-CoA synthetase 5 required for sporopollenin biosynthesis. We identified the rice homolog of ACOS5 as OsACOS12. The CRISPR/Cas9-mediated OsACOS12 knockout mutant has complete male sterility due to a defect in pollen wall formation. β-Glucuronidase reporter gene analysis and RNA in situ hybridization indicated that OsACOS12 was specifically expressed in tapetum and microspores. The subcellular localization of OsACOS12-YFP demonstrated that OsACOS12 protein was primarily localized in the endoplasmic reticulum and nucleus. Our results suggest that OsACOS12 plays a critical and conserved role in pollen wall formation and pollen development and has implications in rice breeding.     

Frugivore assemblage of <Emphasis Type="Italic">Ficus superba</Emphasis> in a warm-temperate forest in Yakushima,Japan

Understanding fig consumption patterns is important because figs are regarded as a keystone resource for many frugivorous species in the tropics. While much work on fig consumption has been conducted in tropical regions, temperate forests are particularly interesting for study owing to pronounced seasonal variations in temperature and community-level fruiting phenology. We studied frugivore consumption of Ficus superba (Miq.) Miq. var. japonica Miq syconia in a warm-temperate forest in Yakushima, southern Japan. We conducted 141 4-h focal observations of fruiting F. superba trees over 12 months. We aimed to assess the relative quantitative contribution of each species of frugivore to F. superba consumption over a year as well as factors affecting seasonal variation in consumption. Japanese macaques were by far the most important F. superba syconia consumer (87.6 %), followed by brown-eared bulbuls (5.0 %), and varied tits (4.2 %). Japanese macaques increased their F. superba consumption when the temperature was high and fruit availability (F. superba and other species) was low. Macaques seemed to avoid searching for rare F. superba trees during winter and used F. superba syconia as a fallback food during fruit scarcity. Birds showed the opposite pattern: they increased F. superba syconia consumption when the temperature was low and fruit availability was high. This was probably because birds eat insects as their main food in the summer and switch to fruit as autumn turns to winter.     

Differentiation of the pollen size in five representatives of <Emphasis Type="Italic">Taraxacum</Emphasis> sect. <Emphasis Type="Italic">Palustria</Emphasis>

Measurements of the pollen size in 5 species of Taraxacum sect. Palustria at three levels of ploidy: 2n = 3x = 24 (T. paucilobum), 2n = 4x = 32 (T. vindobonense, T. trilobifolium), 2n = 5x = 40 (T. mendax) and one taxon of unknown number of chromosomes 2n = ? (T. portentosum) are presented in this paper. Obtained results indicate a lack of distinct positive correlation between the pollen size and ploidy in the studied group of plants. Distinct relationship was, however, found between ploidy and the range of pollen size and shape variability. Most variable were the pollen grains of triploid T. paucilobum and the least — those in pentaploid T. mendax. Ranges of pollen variability in tetraploid T. trilobifolium and T. vindobonense and in T. portentosum of unknown number of chromosomes showed intermediate values.     

Ectopic expression of cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.) <Emphasis Type="Italic">CsTIR</Emphasis>/<Emphasis Type="Italic">AFB</Emphasis> genes enhance salt tolerance in transgenic <Emphasis Type="Italic">Arabidopsis</Emphasis>

Auxin receptors TIR1/AFBs play an essential role in a series of signaling network cascades. These F-box proteins have also been identified to participate in different stress responses via the auxin signaling pathway in Arabidopsis. Cucumber (Cucumis sativus L.) is one of the most important crops worldwide, which is also a model plant for research. In the study herein, two cucumber homologous auxin receptor F-box genes CsTIR and CsAFB were cloned and studied for the first time. The deduced amino acid sequences showed a 78% identity between CsTIR and AtTIR1 and 76% between CsAFB and AtAFB2. All these proteins share similar characteristics of an F-box domain near the N-terminus, and several Leucine-rich repeat regions in the middle. Arabidopsis plants ectopically overexpressing CsTIR or CsAFB were obtained and verified. Shorter primary roots and more lateral roots were found in these transgenic lines with auxin signaling amplified. Results showed that expression of CsTIR/AFB genes in Arabidopsis could lead to higher seeds germination rates and plant survival rates than wild-type under salt stress. The enhanced salt tolerance in transgenic plants is probably caused by maintaining root growth and controlling water loss in seedlings, and by stabilizing life-sustaining substances as well as accumulating endogenous osmoregulation substances. We proposed that CsTIR/AFB-involved auxin signal regulation might trigger auxin mediated stress adaptation response and enhance the plant salt stress resistance by osmoregulation.