Interfamily Grafted Hybrids Vitis vinifera/Schisandra chinensis Resulted in Transcriptomic, Phenotypic, and Metabolic Changes.

Long-distance transfer of genetic material and metabolites between rootstock and scions is well documented in homo-grafted hybrids but has rarely been reported in genetically-distant grafts where the rootstock and scion belong to different families. In this study, we grafted Vitis vinifera scions onto Schisandra chinensis stocks and obtained 20 vegetative hybrids, Vitis vinifera/Schisandra chinensis (Vs). After 25 years of growth, we found that the phenotypes of the leaves, internodes, and fruits of the Vs hybrids above the graft union resembled an intermediate phenotype between V. vinifera and S. chinensis, and the new traits were stable when propagated vegetatively. We further analyzed genetic differences between Vv plants and Vs hybrids using high-throughput sequencing, while metabolomes were analyzed by liquid chromatography-mass spectrometry (LC-MS). We found a total of 2113 differentially expressed genes (DEGs). GO annotation and KEGG pathway enrichment analysis showed that these DEGs enriched mainly in oxidation-reduction and metabolic processes. Seventy-nine differentially expressed miRNAs (DEMs) containing 27 known miRNAs and 52 novel miRNAs were identified. A degradation analysis detected 840 target genes corresponding to 252 miRNAs, of which 12 DEMs and their corresponding target gene expression levels were mostly negatively correlated. Furthermore, 1188 differential metabolic compounds were identified. In particular, in Vs hybrids, the abundance of the metabolites schizandrin and gomisin as the main medicinal ingredients in S. chinensis were down-regulated and up-regulated, respectively. Our data demonstrated the effects of interfamily grafts on the phenotype, transcript profile and metabolites of the scion, and also provided new insight into the genetic, phenotypic, and metabolic plasticity associated with genetically distant grafted hybrids.

Chromosome-Level Genome Assembly and Population Genomic Analyses Reveal Geographic Variation and Population Genetic Structure of Prunus tenella.

Prunus tenella is a rare and precious relict plant in China. It is an important genetic resource for almond improvement and an indispensable material in ecological protection and landscaping. However, the research into molecular breeding and genetic evolution has been severely restricted due to the lack of genome information. In this investigation, we created a chromosome-level genomic pattern of P. tenella, 231 Mb in length with a contig N50 of 18.1 Mb by Hi-C techniques and high-accuracy PacBio HiFi sequencing. The present assembly predicted 32,088 protein-coding genes, and an examination of the genome assembly indicated that 94.7% among all assembled transcripts were alignable to the genome assembly; most (97.24%) were functionally annotated. By phylogenomic genome comparison, we found that P. tenella is an ancient group that diverged approximately 13.4 million years ago (mya) from 13 additional closely related species and about 6.5 Mya from the cultivated almond. Collinearity analysis revealed that P. tenella is highly syntenic and has high sequence conservation with almond and peach. However, this species also exhibits many presence/absence variants. Moreover, a large inversion at the 7588 kb position of chromosome 5 was observed, which may have a significant association with phenotypic traits. Lastly, population genetic structure analysis in eight different populations indicated a high genetic differentiation among the natural distribution of P. tenella. This high-quality genome assembly provides critical clues and comprehensive information for the systematic evolution, genetic characteristics, and functional gene research of P. tenella. Moreover, it provides a valuable genomic resource for in-depth study in protection, developing, and utilizing P. tenella germplasm resources.

Genome-Wide Analysis of DREB Family Genes and Characterization of Cold Stress Responses in the Woody Plant Prunus nana.

Dehydration response element binding factor (DREB) is a family of plant-specific transcription factors, whose members participate in the regulation of plant responses to various abiotic stresses. Prunus nana, also known as the wild almond, is a member of the Rosaceae family that is rare and found to grow in the wild in China. These wild almond trees are found in hilly regions in northern Xinjiang, and exhibit greater drought and cold stress resistance than cultivated almond varieties. However, the response of P. nana DREBs (PnaDREBs) under low temperature stress is still unclear. In this study, 46 DREB genes were identified in the wild almond genome, with this number being slightly lower than that in the sweet almond (Prunus dulcis cultivar 'Nonpareil'). These DREB genes in wild almond were separated into two classes. All PnaDREB genes were located on six chromosomes. PnaDREB proteins that were classified in the same groups contained specific shared motifs, and promoter analyses revealed that PnaDREB genes harbored a range of stress-responsive elements associated with drought, low-temperature stress, light responsivity, and hormone-responsive cis-regulatory elements within their promoter regions. MicroRNA target site prediction analyses also suggested that 79 miRNAs may regulate the expression of 40 of these PnaDREB genes, with PnaDREB2. To examine if these identified PnaDREB genes responded to low temperature stress, 15 of these genes were selected including seven homologous to Arabidopsis C-repeat binding factor (CBFs), and their expression was assessed following incubation for 2 h at 25 °C, 5 °C, 0 °C, -5 °C, or -10 °C. In summary, this analysis provides an overview of the P. nana PnaDREB gene family and provides a foundation for further studies of the ability of different PnaDREB genes to regulate cold stress responses in almond plants.

Complete chloroplast genome of the oil-bearing shrub Staphylea bumalda DC (Staphyleaceae).

Staphylea bumalda DC, belonging to family Staphyleaceae, is a woody understory tree that is both edible and medicinal and produces oil with high economic value. This study reports the first complete chloroplast genome sequence of S. bumalda. The complete chloroplast genome sequence of S. bumalda is 160,319 bp in length with an overall GC content of 32.79%, which is composed of a large single-copy region (LSC: 89,401 bp), a small single-copy region (SSC: 18,834 bp), and two inverted repeat regions (IR: 26,042 bp). A total of 130 genes were predicted in this genome, including 85 protein-coding genes, 37 tRNA genes, and eight rRNA genes. The phylogenetic analysis based on 14 complete chloroplast sequences from related species revealed that S. bumalda is a sister to S. holocarpa.

Genome-Wide Identification and Function of Aquaporin Genes During Dormancy and Sprouting Periods of Kernel-Using Apricot (Prunus armeniaca L.).

Aquaporins (AQPs) are essential channel proteins that play a major role in plant growth and development, regulate plant water homeostasis, and transport uncharged solutes across biological membranes. In this study, 33 AQP genes were systematically identified from the kernel-using apricot (Prunus armeniaca L.) genome and divided into five subfamilies based on phylogenetic analyses. A total of 14 collinear blocks containing AQP genes between P. armeniaca and Arabidopsis thaliana were identified by synteny analysis, and 30 collinear blocks were identified between P. armeniaca and P. persica. Gene structure and conserved functional motif analyses indicated that the PaAQPs exhibit a conserved exon-intron pattern and that conserved motifs are present within members of each subfamily. Physiological mechanism prediction based on the aromatic/arginine selectivity filter, Froger's positions, and three-dimensional (3D) protein model construction revealed marked differences in substrate specificity between the members of the five subfamilies of PaAQPs. Promoter analysis of the PaAQP genes for conserved regulatory elements suggested a greater abundance of cis-elements involved in light, hormone, and stress responses, which may reflect the differences in expression patterns of PaAQPs and their various functions associated with plant development and abiotic stress responses. Gene expression patterns of PaAQPs showed that PaPIP1-3, PaPIP2-1, and PaTIP1-1 were highly expressed in flower buds during the dormancy and sprouting stages of P. armeniaca. A PaAQP coexpression network showed that PaAQPs were coexpressed with 14 cold resistance genes and with 16 cold stress-associated genes. The expression pattern of 70% of the PaAQPs coexpressed with cold stress resistance genes was consistent with the four periods [Physiological dormancy (PD), ecological dormancy (ED), sprouting period (SP), and germination stage (GS)] of flower buds of P. armeniaca. Detection of the transient expression of GFP-tagged PaPIP1-1, PaPIP2-3, PaSIP1-3, PaXIP1-2, PaNIP6-1, and PaTIP1-1 revealed that the fusion proteins localized to the plasma membrane. Predictions of an A. thaliana ortholog-based protein-protein interaction network indicated that PaAQP proteins had complex relationships with the cold tolerance pathway, PaNIP6-1 could interact with WRKY6, PaTIP1-1 could interact with TSPO, and PaPIP2-1 could interact with ATHATPLC1G. Interestingly, overexpression of PaPIP1-3 and PaTIP1-1 increased the cold tolerance of and protein accumulation in yeast. Compared with wild-type plants, PaPIP1-3- and PaTIP1-1-overexpressing (OE) Arabidopsis plants exhibited greater tolerance to cold stress, as evidenced by better growth and greater antioxidative enzyme activities. Overall, our study provides insights into the interaction networks, expression patterns, and functional analysis of PaAQP genes in P. armeniaca L. and contributes to the further functional characterization of PaAQPs.

Insights Into the Molecular Mechanisms of Late Flowering in Prunus sibirica by Whole-Genome and Transcriptome Analyses.

Freezing during the flowering of Prunus sibirica is detrimental to fruit production. The late flowering (LF) type, which is delayed by 7-15 days compared with the normal flowering (NF) type, avoids damages at low temperature, but the molecular mechanism of LF remains unclear. Therefore, this study was conducted to comprehensively characterize floral bud differentiation. A histological analysis showed that initial floral bud differentiation was delayed in the LF type compared to the NF type. Genome-wide associated studies (GWAS) showed that a candidate gene (PaF106G0600023738.01) was significantly associated with LF type. It was identified as trehalose-6-phosphate phosphatase (PsTPPF), which is involved in trehalose-6-phosphate (Tre6P) signaling pathway and acts on floral transition. A whole-transcriptome RNA sequencing analysis was conducted, and a total of 6,110 differential expression (DE) mRNAs, 1,351 DE lncRNAs, and 148 DE miRNAs were identified. In addition, 24 DE mRNAs related with floral transition were predicted, and these involved the following: three interactions between DE lncRNAs and DE mRNAs of photoperiod pathway with two mRNAs (COP1, PaF106G0400018289.01 and CO3, MXLOC_025744) and three lncRNAs (CCLR, LTCONS_00031803, COCLR1, LTCONS_00046726, and COCLR2, LTCONS_00046731); one interaction between DE miRNAs and DE mRNAs with one mRNA, encoding trehalose-6-phosphate synthase (PsTPS1, PaF106G0100001132.01), and one miRNA (miRNA167h). Combined with the expression profiles and Tre6P levels, functions of PsTPPF and PsTPS1 in Tre6P regulation were considered to be associated with flowering time. A new network of ceRNAs correlated with LF was constructed, and it consisted of one mRNA (PsTPS1), one lncRNA (TCLR, LTCONS_00034157), and one miRNA (miR167h). This study provided insight into the molecular regulatory mechanism of LF in Prunus sibirica.