Yun-Zhou Lyu

Acer truncatum, originating in China, is an ornamental tree species with high economic value. In September 2022, a new leaf spot disease was observed on seedlings of A. truncatum in a tree nursery from the Jiangsu Academy of Forestry (118°45'517.30″E, 24 31°51'27.94″N) in China. According to statistics, 62.5% of 1600 A. truncatum seedlings suffered from the disease. The first symptoms were black to brown spots appearing on the infected leaves. Subsequently, the spots gradually expanded into larger areas, and finally the entire leaf turned yellow and fell off. The diseased leaves were collected and sections of 3 to 4 mm were excised from the margins between healthy and diseased tissues, surface sterilized in 75% ethanol for 30 sec. and 1.5% NaClO for 90 sec., rinsed three times in sterilized distilled water, plated on potato dextrose agar (PDA) and incubated at 25℃ in darkness. Pure cultures were obtained by monosporic isolation. Six fungal cultures with similar morphological characteristics were obtained from the infected tissues, and they accounted for 70% of the total isolates. Colonies were initially white but turned dark gray following 7 days of incubation at 25°C in the dark. To induce sporulation, colonies were grown on 2% water agar and incubated under UVA light at 25°C for two weeks. The conidiophores produced conidia, and conidia were hyaline, unicellular, nonseptate, ellipsoidal to fusiform, externally smooth, thin-walled, and were 15.3 to 20.4 × 4.5 to 7.4 μm (n=35, counted from the two selected isolates). These characteristics were consistent with the description of Neofusicoccum sp. (Kirk et al. 2008). Isolates YBF2-1 and YBF5-1 were selected as representative for molecular identification. The internal transcribed spacer region (ITS), the translation elongation factor 1-alpha gene (EF1-α), and the beta-tubulin gene (TUB2), using the primer pairs ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Alves et al. 2008), and Bt2a/Bt2b (Glass and Donaldson 1995) were amplified, respectively. The obtained ITS (GenBank Accession No. PP980685, PQ222752), EF1-α (No. PQ009204, PQ227810), and TUB2 sequences (No. PP993456, PQ227811) all showed >99% homology with several GenBank sequences of Neofusicoccum parvum (MK370685, KC818612 for ITS; MH118932, KJ126847 for EF1-α; and MN318109, OL456719 for TUB2, respectively). A neighbor-joining phylogenetic tree was generated by combining all sequenced loci in MEGA7. The two isolates were identified as N. parvum. To test pathogenicity, 15 leaves on three one-month-old A. truncatum seedlings (five leaves from each seedling) were wounded with a sterile needle inoculated with 20 μL conidia suspension (1×106 spores/mL) on the left sides of the leaves, using isolate YBF2-1, while the same size droplet of sterilized water was used on the right sides of leaves. Each plant was separately covered with clear polyethylene bags to maintain about 80% relative humidity at 25℃. After 5 days of inoculation, typical symptoms were found on the left sides of treated leaves, and no symptoms occurred on the right sides of the leaves (the control). The inoculation experiment was conducted three times. Subsequently, the same fungus was reisolated and identified from six leaves of three inoculated seedlings. This is the first report of N. parvum on A. truncatum in the world, and it provides an important reference for the biology and epidemiology of N. parvum.

Ulmus parvifolia Jacq. is an important tree with ornamental value, which is widely planted in Hebei and southern regions of China. In September 2022, a leaf spot symptom was observed on about approximately 20% U. parvifolia seedlings growing a tree farm (20000 m2) of Jiangsu Academy of Forestry (118°45'57.30″E, 31°51'27. 94″N). Gray to black spots appeared on leaves of seedlings. Five diseased leaves were collected from five different seedlings. The pieces were excised from the margins between healthy and diseased tissues, surface sterilized in 75% ethanol for 30 s and then in 1.5% NaClO for 90 s, rinsed three times in sterilized distilled water, plated on potato dextrose agar (PDA) and incubated at 25℃ in the darkness. Pure cultures were obtained by monosporic isolation. Six isolates with identical morphological features and the internal transcribed spacer (ITS) sequences were obtained (the isolate rate of 67%), and identified as Alternaria sp. A representative isolate, LY-1-1 was used for the further study. The colony of LY-1-1, growing on PDA was cotton-like and brown in color with gray-white aerial hyphae on their surfaces, and its reverse was dark grey. The conidia were ovate to pear-shaped, brown in color, with 1 to 4 transverse septa and 0 to 1 longitudinal septa, parietal cells extending into the beak, and measured 7.1 to 12.5×3.8 to 7.1 µm (n=35). These characteristics were consistent with the description of Alternaria sp. (Simmons 2007). The regions of ITS, large subunit ribosomal RNA (LSU), small subunit ribosomal RNA (SSU), anonymous region OPA10-2 genomic sequence (OPA10-2), Alternaria 1 major allergen (Alta1), glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and translation elongation factor 1-alpha (TEF1) genes (GenBank Accession No. OR047916, OR051904, OR047919, OR061065, OR061063, OR061064, and OR061062, respectively) were amplified (White et al. 1990; Woudenberg et al. 2015) and sequenced. These obtained sequences showed 99.86-100% similarity to the ITS (514/515 bp) of A. alternata isolate SPM-2 (OR378581), LSU (801/801 bp) of isolate B9 (OR366492), SSU (1019/1020 bp) of strain LSU0766 (MT000349), OPA10-2 (632/633 bp) of strain 19-1 (MN185000), Alta1 (470/470 bp) of strain CMML21-73 (OQ831518), GAPDH (177/177 bp) of isolate CS36-3 (KY814638), and TEF1 (240/240 bp) of isolate SY-6 (OP980553). A neighbor-joining phylogenetic tree was generated by combining all sequenced loci in MEGA7. The isolate LY-1-1 clustered in the A. alternata clade with 98% bootstrap support. Three 3-month-old U. parvifolia seedlings were wounded with a sterile needle and inoculated with 20 μL conidia suspension (1×106 spores/mL) on the left sides of leaves. Inoculation on the right side with 20 µL of sterile water was treated as a control. All inoculated plants were incubated in a greenhouse at 25℃, 80% relative humidity, and a 12-h light/dark cycle. The experiment was repeated three times. After 5 days of inoculation, typical gray to black spots were found on the left sides of all inoculated leaves, and the control did not have any leaf spot symptoms. Subsequently, the same fungus was reisolated and identified based on morphological and molecular traits, fulfilling Koch's postulates. The A. alternata has been reported to cause leaf spot on pecan (Wu et al. 2020), fruit spot on olive (Alam et al. 2019) and fruit rot on lychee (Alam et al. 2017). However, there are no other reports of A. alternata on U. parvifolia in the world. Thus, this study provides an important reference for the biology, epidemiology of A. alternata.

Pecan (Carya illinoinensis) is an important oilseed nut and is rich in fatty acids and flavonols. Pecan fatty acid has significantly edible, industrial, and clinical value. To investigate the dynamic patterns and compositions of fatty acid, and the molecular mechanism that controls fatty acid accumulation in pecan, lipidomic and transcriptomic analyses were performed to determine lipid profiles and gene expression in pecan’s fatty acid biosynthesis pathway. In the present study, compared to cultivars ‘Caddo’ and ‘Y-01’, ‘Mahan’ formed larger and heavier embryos and accumulated higher oil content. Lipidomic analysis showed that fatty acid and (O-acyl)-1-hydroxy fatty acid contents were higher in ‘Mahan’ at the mature stage. Based on full-length and comparative RNA-Seq, differential expression gene enrichment analysis revealed that many functional genes participated in the pathways of ‘fatty acid biosynthesis’, ‘fatty acid metabolism’, and ‘linoleic acid metabolism’. High fatty acid accumulation model from ‘Mahan’ demonstrated that key enzyme encoding genes played an important role in regulating fatty acid biosynthesis. Co-expression module analysis indicated that several transcription factors (MYB, TCP, bHLH, Dof, ERF, NAC) were involved in fatty acid accumulation by regulating the expression of functional genes, and real-time quantitative PCR verification proved that these transcription factors had a high correlation with pecan fatty acid accumulation pattern. These findings provided an insight into the molecular mechanism of fatty acid accumulation in C. illinoinensis embryo, which contributes to pecan oil yielding and pecan molecular breeding.

Background: The accumulation of fatty acids in plants covers a wide range of functions in plant physiology and thereby affects adaptations and characteristics of species. As the famous woody oilseed crop, Acer truncatum accumulates unsaturated fatty acids and could serve as the model to understand the regulation and trait formation in oil-accumulation crops. Here, we performed Ribosome footprint profiling combing with a multi-omics strategy towards vital time points during seed development, and finally constructed systematic profiling from transcription to proteomes. Additionally, we characterized the small open reading frames (ORFs) and revealed that the translational efficiencies of focused genes were highly influenced by their sequence features. Results: The comprehensive multi-omics analysis of lipid metabolism was conducted in A. truncatum. We applied the Ribo-seq and RNA-seq techniques, and the analyses of transcriptional and translational profiles of seeds collected at 85 and 115 DAF were compared. Key members of biosynthesis-related structural genes (LACS, FAD2, FAD3, and KCS) were characterized fully. More meaningfully, the regulators (MYB, ABI, bZIP, and Dof) were identified and revealed to affect lipid biosynthesis via post-translational regulations. The translational features results showed that translation efficiency tended to be lower for the genes with a translated uORF than for the genes with a non-translated uORF. They provide new insights into the global mechanisms underlying the developmental regulation of lipid metabolism. Conclusions: We performed Ribosome footprint profiling combing with a multi-omics strategy in A. truncatum seed development, which provides an example of the use of Ribosome footprint profiling in deciphering the complex regulation network and will be useful for elucidating the metabolism of A. truncatum seed oil and the regulatory mechanisms.

"‘Chongtian’: A New Zelkova schneideriana cultivar" published on Apr 2023 by American Society for Horticultural Science.

The Chinese elm is an important tree ecologically; however, little is known about its genetic diversity and adaptation mechanisms. In this study, a total of 107 individuals collected from seven natural populations in eastern China were investigated by specific locus amplified fragment sequencing (SLAF-seq). Based on the single nucleotide polymorphisms (SNPs) detected by SLAF-seq, genetic diversity and markers associated with climate variables were identified. All seven populations showed medium genetic diversity, with PIC values ranging from 0.2632 to 0.2761. AMOVA and Fst indicated that a low genetic differentiation existed among populations. Environmental association analyses with three climate variables (annual rainfall, annual average temperature, and altitude) resulted in, altogether, 43 and 30 putative adaptive loci by Bayenv2 and LFMM, respectively. Five adaptive genes were annotated, which were related to the functions of glycosylation, peroxisome synthesis, nucleic acid metabolism, energy metabolism, and signaling. This study was the first on the genetic diversity and local adaptation in Chinese elms, and the results will be helpful in future work on molecular breeding.