Prenatal diagnosis of cleidocranial dysplasia: Case report on two cases with a negative family history.

Introduction: Cleidocranial dysplasia (CCD) is a rare autosomal dominant skeletal dysplasia that presents with abnormalities in the craniofacial region, teeth, and clavicles and is linked to RUNX2 mutation. Prenatal diagnoses of CCD have rarely been reported, and most of these cases have a positive family history. Here we report two prenatally diagnosed CCD cases without a positive family history. We conducted a literature review to summarize the prenatal sonographic findings of CCD. Case reports: Case 1 (a 26-year-old woman): ultrasound at 13 weeks showed a thickened nuchal translucency with absent nasal bones and poor ossifications in the cranium and vertebrae. Genetic testing confirmed a frame shift deletion of RUNX2. Case 2 (a 27-year-old woman): ultrasound at 32 weeks showed potential fetal skeletal dysplasia, with inadequate skull ossification, mild ossified bilateral clavicles, and RUNX2 frameshift deletion mutation. Both cases were diagnosed with CCD and the parents chose pregnancy termination. Conclusion: These cases underscore the importance of sonographic examination for prenatal CCD diagnosis with a negative family history. By reviewing previous cases, we concluded that combining NB hypoplasia, clavicle and skull hypoplasia, and shortened long bones may be effective for early screening for CCD. Prenatal diagnosis is crucial for guiding medical decisions.

The NAC transcription factor MdNAC29 negatively regulates drought tolerance in apple.

Drought stress is an adverse stimulus that affects agricultural production worldwide. NAC transcription factors are involved in plant development and growth but also play different roles in the abiotic stress response. Here, we isolated the apple MdNAC29 gene and investigated its role in regulating drought tolerance. Subcellular localization experiments showed that MdNAC29 was localized to the nucleus and transcription was induced by the PEG treatment. Over-expression of MdNAC29 reduced drought tolerance in apple plants, calli, and tobacco, and exhibited higher relative conductivity, malondialdehyde (MDA) content, and lower chlorophyll content under drought stress. The transcriptomic analyses revealed that MdNAC29 reduced drought resistance by modulating the expression of photosynthesis and leaf senescence-related genes. The qRT-PCR results showed that overexpression of MdNAC29 repressed the expression of drought-resistance genes. Yeast one-hybrid and dual-luciferase assays demonstrated that MdNAC29 directly repressed MdDREB2A expression. Moreover, the yeast two-hybrid and bimolecular fluorescence complementation assays demonstrated that MdNAC29 interacted with the MdPP2-B10 (F-box protein), which responded to drought stress, and MdPP2-B10 enhanced the repressive effect of MdNAC29 on the transcriptional activity of the MdDREB2A. Taken together, our results indicate that MdNAC29 is a negative regulator of drought resistance, and provide a theoretical basis for further molecular mechanism research.

PpMYB52 negatively regulates peach bud break through the gibberellin pathway and through interactions with PpMIEL1.

Bud dormancy, which enables damage from cold temperatures to be avoided during winter and early spring, is an important adaptive mechanism of deciduous fruit trees to cope with seasonal environmental changes and temperate climates. Understanding the regulatory mechanism of bud break in fruit trees is highly important for the artificial control of bud break and the prevention of spring frost damage. However, the molecular mechanism underlying the involvement of MYB TFs during the bud break of peach is still unclear. In this study, we isolated and identified the PpMYB52 (Prupe.5G240000.1) gene from peach; this gene is downregulated in the process of bud break, upregulated in response to ABA and downregulated in response to GA. Overexpression of PpMYB52 suppresses the germination of transgenic tomato seeds. In addition, Y2H, Bimolecular fluorescence complementation (BiFC) assays verified that PpMYB52 interacts with a RING-type E3 ubiquitin ligase, PpMIEL1, which is upregulated during bud break may positively regulate peach bud break by ubiquitination-mediated degradation of PpMYB52. Our findings are the first to characterize the molecular mechanisms underlying the involvement of MYB TFs in peach bud break, increasing awareness of dormancy-related molecules to avoid bud damage in perennial deciduous fruit trees.

The apple GARP family gene MdHHO3 regulates the nitrate response and leaf senescence.

The regulation of plant gene expression by nitrate is a complex regulatory process. Here, we identified 90 GARP family genes in apples by genome-wide analysis. As a member of the GARP gene family, the expression of MdHHO3 (Malus domestica HYPERSENSITIVITY TO LOW PHOSPHATE-ELICITED PRIMARY ROOT SHORTENING1 HOMOLOG 3) is upregulated under N (nitrogen) supply. The results of DNA-binding site analysis and electrophoretic mobility shift assays (EMSA) showed that MdHHO3 binds to the motif-containing GAATC. Furthermore, MdHHO3 binds to its promoter sequence and inhibits its activity. In addition, the overexpression of MdHHO3 in apple calli resulted in less accumulation of nitrate in 35S:MdHHO3-GFP calli and downregulated the expression of the nitrate transport-related genes but upregulated the expression of the nitrate assimilation-related genes. Similarly, the expression of the nitrate transport-related genes was downregulated and the expression of the nitrate assimilation-related genes was upregulated in MdHHO3 overexpression Arabidopsis and tobacco plants. Interaction experiments showed that MdHHO3 could bind to the promoter MdNRT2.1 (NITRATE TRANSPORTER 2.1) and negatively regulate its expression. Moreover, the exposure of MdHHO3-overexpressing Arabidopsis and tobacco to nitrate deficiency resulted in an early senescence phenotype as compared to the WT plants. These results show that MdHHO3 can not only negatively regulate nitrate accumulation in response to nitrate but also promote early leaf senescence under nitrate deficiency. This information may be useful to further reveal the mechanism of the nitrate response and demonstrates that nitrate deficiency induces leaf senescence in apples.

Prunus persica transcription factor PpNAC56 enhances heat resistance in transgenic tomatoes.

Members of the NAC (NAM, ATAF1,2 and CUC2) transcription factor family are involved in numerous processes of plant growth and development and play an important role in the response to abiotic stresses such as salinity, drought and heat, but little research on this topic has been done in peach. In this study, we analyzed the expression patterns of PpNAC56 under abiotic stress and found that PpNAC56 responded to high-temperature stress. To verify the function of PpNAC56, we overexpressed this gene in tomato plants and found that, compared with WT plants, the transgenic tomato plants could accumulate more osmoregulatory substances after high-temperature treatment and thus were more heat resistance. Then, using Y2H, BIFC, and pull-down assays, we found that PpNAC56 could interact with PpMIEL1. In addition, Y1H and dual-luciferase assays verified that PpNAC56 could activate the expression of PpHSP17.4 and PpSnRK2D. The above experimental results demonstrate that PpNAC56 plays an important role in the plant response to heat stress.

Genome-wide identification and characterization of the Prunus persica ferredoxin gene family and its role in improving heat tolerance.

Ferredoxin is involved in many biological processes, such as carbon fixation, nitrogen assimilation, chlorophyll metabolism, and fatty acid synthesis, and it plays a role in plant resistance to stress. However, the functions of Fds in peach during stress are unclear. In this study, 11 members of the peach Fd gene family were identified and divided into six groups (I- VI). We carried out bioinformatics analysis on these sequences, analyzed the physical and chemical properties of PpFd protein and the cis-elements in its promoter region, and predicted and compared the differences in gene structure and conserved protein motifs among groups. The results showed that the PpFd protein was highly conserved in plant species. In addition, overexpression of PpFd08 significantly increased the tolerance of transgenic tomato to high-temperature stress. The transcriptome analysis and qRT-PCR results of PpFd08 transgenic apple calli showed that PpFd08 might enhance heat resistance by modulating the expression of heat tolerance related genes. The results of this study provide a new understanding for the further study of the function of PpFd protein in peach and a candidate gene for improving the heat resistance of peach.

Prunus persica Terpene Synthase PpTPS1 Interacts with PpABI5 to Enhance Salt Resistance in Transgenic Tomatoes.

Terpene synthase (TPS) is related to the production of aromatic substances, but there are few studies on the impact of abiotic stress on TPS and its molecular mechanism, especially in peaches. This study found that salt resistance and abscisic acid (ABA) sensitivity of transgenic tomatoes were enhanced by overexpression of PpTPS1. Moreover, it was found that PpTPS1 interacted with and antagonized the expression of the bZIP transcription factor ABA INSENSITIVE 5 (PpABI5), which is thought to play an important role in salt suitability. In addition, PpTCP1, PpTCP13, and PpTCP15 were found to activate the expression of PpTPS1 by yeast one-hybrid (Y1H) and dual-luciferase assays, and they could also be induced by ABA. In summary, PpTPS1 may be involved in the ABA signaling regulatory pathway and play an important role in salt acclimation, providing a new reference gene for the improvement of salt resistance in peaches.

OVATE Family Protein PpOFP1 Physically Interacts With PpZFHD1 and Confers Salt Tolerance to Tomato and Yeast.

The OVATE family protein (OFP) genes (OFPs) have been shown to respond to salt stress in plants. However, the regulatory mechanism for salt tolerance of the peach (Prunus persica) OFP gene PpOFP1 has not been elucidated. In this study, using yeast two-hybrid screening, we isolated a nucleus-localized ZF-HD_dimer domain protein PpZFHD1, which interacts with the PpOFP1 protein in the peach cultivar "Zhongnongpan No.10". A segmentation experiment further suggested that the interaction happens more specifically between the N-terminal, contains ZF-HD_dimer domain, of PpZFHD1 and the C-terminal, consists of OVATE domain, of PpOFP1. Additionally, quantitative real-time polymerase chain reaction (qRT-PCR) experiments indicate that transcription of these two genes are induced by 200 mmol/L (mM) NaCl treatment. Heterogeneous transformation experiments suggested that the growth status of transformed yeast strain over-expressing each of these two genes was more robust than that of control (CK). Furthermore, transgenic tomato plants over-expressing PpOFP1 were also more robust. They had a higher content of chlorophyll, soluble proteins, soluble sugars, and proline. Activities of the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in these plants were higher, and tissues from these plants exhibited a lower relative conductivity and malondialdehyde (MDA) content. These results suggest that PpOFP1 physically interacts with PpZFHD1 and confers salt tolerance to tomato and yeast, thus revealing a novel mechanism for regulating salt tolerance in peach and other perennial deciduous trees.

Chromosome-level genome assemblies of five Prunus species and genome-wide association studies for key agronomic traits in peach.

Prunus species include many important perennial fruit crops, such as peach, plum, apricot, and related wild species. Here, we report de novo genome assemblies for five species, including the cultivated species peach (Prunus persica), plum (Prunus salicina), and apricot (Prunus armeniaca), and the wild peach species Tibetan peach (Prunus mira) and Chinese wild peach (Prunus davidiana). The genomes ranged from 240 to 276 Mb in size, with contig N50 values of 2.27-8.30 Mb and 25,333-27,826 protein-coding gene models. As the phylogenetic tree shows, plum diverged from its common ancestor with peach, wild peach species, and apricot ~7 million years ago (MYA). We analyzed whole-genome resequencing data of 417 peach accessions, called 3,749,618 high-quality SNPs, 577,154 small indels, 31,800 deletions, duplications, and inversions, and 32,338 insertions, and performed a structural variant-based genome-wide association study (GWAS) of key agricultural traits. From our GWAS data, we identified a locus associated with a fruit shape corresponding to the OVATE transcription factor, where a large inversion event correlates with higher OVATE expression in flat-shaped accessions. Furthermore, a GWAS revealed a NAC transcription factor associated with fruit developmental timing that is linked to a tandem repeat variant and elevated NAC expression in early-ripening accessions. We also identified a locus encoding microRNA172d, where insertion of a transposable element into its promoter was found in double-flower accessions. Thus, our efforts have suggested roles for OVATE, a NAC transcription factor, and microRNA172d in fruit shape, fruit development period, and floral morphology, respectively, that can be connected to traits in other crops, thereby demonstrating the importance of parallel evolution in the diversification of several commercially important domesticated species. In general, these genomic resources will facilitate functional genomics, evolutionary research, and agronomic improvement of these five and other Prunus species. We believe that structural variant-based GWASs can also be used in other plants, animal species, and humans and be combined with deep sequencing GWASs to precisely identify candidate genes and genetic architecture components.

Overexpression of the Peach Transcription Factor Early Bud-Break 1 Leads to More Branches in Poplar.

Shoot branching is an important adaptive trait that determines plant architecture. In a previous study, the Early bud-break 1 (EBB1) gene in peach (Prunus persica var. nectarina) cultivar Zhongyou 4 was transformed into poplar (Populus trichocarpa). PpEBB1-oe poplar showed a more branched phenotype. To understand the potential mechanisms underlying the EBB1-mediated branching, transcriptomic and proteomics analyses were used. The results showed that a large number of differentially expressed genes (DEGs)/differentially expressed proteins (DEPs) associated with light response, sugars, brassinosteroids (BR), and nitrogen metabolism were significantly enriched in PpEBB1-oe poplar. In addition, contents of sugars, BR, and amino acids were measured. Results showed that PpEBB1 significantly promoted the accumulation of fructose, glucose, sucrose, trehalose, and starch. Contents of brassinolide (BL), castasterone (CS), and 6-deoxocathasterone (6-deoxoCS) were all significantly changed with overexpressing PpEBB1. Various types of amino acids were measured and four of them were significantly improved in PpEBB1-oe poplar, including aspartic acid (Asp), arginine (Arg), cysteine (Cys), and tryptohpan (Trp). Taken together, shoot branching is a process controlled by a complex regulatory network, and PpEBB1 may play important roles in this process through the coordinating multiple metabolic pathways involved in shoot branching, including light response, phytohormones, sugars, and nitrogen.

BTB-TAZ Domain Protein PpBT3 modulates peach bud endodormancy by interacting with PpDAM5.

The dormancy-associated MADS-box (DAM) gene DAM5 has crucial roles in bud endodormancy; however, the molecular regulatory mechanism of PpDAM5 in peach (Prunus persica) has not been elucidated. In this study, using yeast two-hybrid screening, we isolated a BTB-TAZ Domain Protein PpBT3, which interacts with PpDAM5 protein, in the peach cultivar 'Chun xue'. As expected, we found that abscisic acid (ABA) maintained bud endodormancy and induced expression of the PpDAM5 gene, and that over-expressing PpDAM5 in Arabidopsis thaliana repressed seed germination. In contrast, over-expressing PpBT3 in A. thaliana promoted seed germination, and conferred resistance to ABA-mediated germination inhibition. Additionally, a qRT-PCR (quantitative real-time polymerase chain reaction) experiment suggested that the transcript level of PpBT3 gradually increased towards the endodormancy release period, which is the opposite trend of the expression pattern of PpDAM5. Our results suggest that PpBT3 modulates peach bud endodormancy by interacting with PpDAM5, thus revealing a new mechanism for regulating bud dormancy of perennial deciduous trees.

Auxin alters sodium ion accumulation and nutrient accumulation by playing protective role in salinity challenged strawberry.

High salinity in soil affects the strawberry production and fruit quality. Auxin-primed plants have enhanced responses to soil salinization. In this study, we report that exogenous application of IAA can partially relieve stress responses of strawberry seedlings. Cytological analysis showed that the ultrastructure of root tip and leaf cells in strawberry seedlings were altered under high salinity condition, which was partially recovered after the application of IAA. The study showed that the ultrastructure of root tip and leaf cells in strawberry seedlings were altered under salt stress condition, which was partially recovered after the application of IAA. Exogenous IAA ameliorated deleterious effects on seedling growth under salinity were attributed to accelerated Na+ fluxes, decreased the contents of Na+ to maintain the ion homeostasis, protect root growth, and promote the absorption of nutrients for improved photosynthetic efficiency in strawberry.

PpEBB1 directly binds to the GCC box-like element of auxin biosynthesis related genes.

EARLY BUD-BREAK 1 (EBB1) can promote bud break, and this function is likely conserved in woody plants. To get a more comprehensive understand of its function, peach (Prunus persica var. nectarina cultivar Zhongyou 4) PpEBB1 was overexpressed in Arabidopsis; the resultant phenotypes, including curved leaves, abnormal development of floral organs and low seed set, were similar to those of DORNRÖSCHEN-LIKE (DRNL) overexpression, indicating that PpEBB1 was a putative ortholog of AtDRNL. PpEBB1 bound to the GCC box-like element in the STYLISH1/SHI RELATED SEQUENCE5 (STY1/SRS5) promoter of peach, which has been proposed to occur in Arabidopsis as well. A GCC box-like element was also found in the YUCCA1 (YUC1) promoter, and PpEBB1 could bind to this element and activate the expression of YUC1. In addition to the elevated auxin content in the PpEBB1-oe plants as observed in our previous study, these results suggest that PpEBB1 can regulate auxin biosynthesis by directly activating related genes. Besides, we screened a zinc finger RING-finger protein, MYB30-INTERACTING E3 LIGASE 1 (PpMIEL1), showing interaction with PpEBB1, suggesting that the stability of PpEBB1 might be influenced by PpMIEL1 through ubiquitination.

PpNUDX8, a Peach NUDIX Hydrolase, Plays a Negative Regulator in Response to Drought Stress.

Drought stress is a serious abiotic stress source that affects the growth and fruit quality of peach trees. However, the molecular mechanism of the NUDIX hydrolase family in peaches in response to drought stress is still unclear. Here, we isolated and identified the PpNUDX8 (Prupe.5G062300.1) gene from the peach NUDIX hydrolase family, and found that PpNUDX8 has a typical NUDIX hydrolase domain. In this study, we performed 15% PEG6000 drought treatment on peach seedlings, and qRT-PCR analysis showed that 15% PEG6000 induced the transcription level of PpNUDX8. Overexpression of PpNUDX8 reduced the tolerance of calli to 4% PEG6000 treatment. Compared with wild-type apple calli, PpNUDX8 transgenic apple calli had a lower fresh weight and higher MDA content. After 15% PEG6000 drought treatment, PpNUDX8 transgenic tobacco had a greater degree of wilting and shorter primary roots than Under control conditions. The chlorophyll, soluble protein, and proline contents in the transgenic tobacco decreased, and the MDA content and relative conductivity increased. At the same time, PpNUDX8 negatively regulated ABA signal transduction and reduced the transcriptional expression of stress response genes. In addition, PpNUDX8 was not sensitive to ABA, overexpression of PpNUDX8 reduced the expression of the ABA synthesis-related gene NCED6 and increases the expression of the ABA decomposition-related gene CYP1 in tobacco, which in turn leads to a decrease in the ABA content in tobacco. In addition, Under control conditions, overexpression of PpNUDX8 destroyed the homeostasis of NAD and reduced nicotinamide adenine dinucleotide (NADH) in tobacco. After 15% PEG6000 drought treatment, the changes in NAD and NADH in PpNUDX8 transgenic tobacco were more severe than those in WT tobacco. In addition, PpNUDX8 also interacted with PpSnRk1γ (Prupe.6G323700.1).

EARLY BUD BREAK 1 triggers bud break in peach trees by regulating hormone metabolism, the cell cycle, and cell wall modifications.

In a previous study we identified EARLY BUD BREAK 1 (EBB1), an ERF transcription factor, in peach (Prunus persica var. nectarina cultivar Zhongyou 4); however, little is known of how PpEBB1 may regulate bud break. To verify the function of PpEBB1 in bud break, PpEBB1 was transiently transformed into peach buds, resulting in early bud break. Bud break occurred earlier in PpEBB1-oe poplar (Populus trichocarpa) obtained by heterologous transformation than in wild type (WT), consistent with the peach bud results, indicating that PpEBB1 can promote bud break. To explore how PpEBB1 affects bud break, differentially expressed genes (DEGs) between WT and PpEBB1-oe poplar plants were identified by RNA-sequencing. The expression of DEGs associated with hormone metabolism, cell cycle, and cell wall modifications changed substantially according to qRT-PCR. Auxin, ABA, and total trans-zeatin-type cytokinin levels were higher in the PpEBB1-oe plants than in WT plants, while the total N6-(Δ 2-isopentenyl)-adenine-type cytokinins was lower. Yeast two-hybrid and bimolecular fluorescence complementation assays verified that a cell wall modification-related protein (PpEXBL1) interacted with PpEBB1 suggesting that PpEBB1 could interact with these cell wall modification proteins directly. Overall, our study proposed a multifaceted explanation for how PpEBB1 regulates bud break and showed that PpEBB1 promotes bud break by regulating hormone metabolism, the cell cycle, and cell wall modifications.

Transcription factor TCP20 regulates peach bud endodormancy by inhibiting DAM5/DAM6 and interacting with ABF2.

The dormancy-associated MADS-box (DAM) genes PpDAM5 and PpDAM6 have been shown to play important roles in bud endodormancy; however, their molecular regulatory mechanism in peach is unclear. In this study, by use of yeast one-hybrid screening, we isolated a TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR transcription factor, PpTCP20, in the peach cultivar 'Zhongyou 4' (Prunus persica var. nectarina). The protein was localized in the nucleus and was capable of forming a homodimer. Electrophoretic mobility shift assays demonstrated that PpTCP20 binds to a GCCCR element in the promoters of PpDAM5 and PpDAM6, and transient dual luciferase experiments showed that PpTCP20 inhibited the expression of PpDAM5 and PpDAM6 as the period of the release of flower bud endodormancy approached. In addition, PpTCP20 interacted with PpABF2 to form heterodimers to regulate bud endodormancy, and the content of abscisic acid decreased with the release of endodormancy. PpTCP20 also inhibited expression of PpABF2 to regulate endodormancy. Taken together, our results suggest that PpTCP20 regulates peach flower bud endodormancy by negatively regulating the expression of PpDAM5 and PpDAM6, and by interacting with PpABF2, thus revealing a novel regulatory mechanism in a perennial deciduous tree.

Corrigendum: Comparison Between Flat and Round Peaches, Genomic Evidences of Heterozygosity Events.

[This corrects the article DOI: 10.3389/fpls.2019.00592.].

Effects of nitrate deficiency on nitrate assimilation and chlorophyll synthesis of detached apple leaves.

Nitrogen is one of the most important nutrients for plant growth and development. Nitrate nitrogen (NO3--N) is the main form of nitrogen taken up by plants. Understanding the effects of exogenous NO3--N on nitrogen metabolism at the gene expression and enzyme activity levels during nitrogen assimilation and chlorophyll synthesis is important for increasing nitrogen utilization efficiency. In this study, cell morphology, NO3--N uptake rates, the expression of key genes related to nitrogen assimilation and chlorophyll synthesis and enzyme activity in apple leaves under NO3--N deficiency were investigated. The results showed that the cell morphology of apple leaves was irreversibly deformed due to NO3--N deficiency. NO3--N was absorbed slightly one day after NO3--N deficiency treatment and effluxed after 3 days. The relative expression of genes encoding nitrogen assimilation enzymes and the activity of such enzymes decreased significantly after 1 day of NO3--N deficiency treatment. After treatment for 14 days, gene expression was upregulated, enzyme activity was increased, and NO3--N content was increased. NO3--N deficiency hindered the transformation of 5-aminobilinic acid (ALA) to porphobilinogen (PBG), suggesting a possible route by which NO3--N levels affect chlorophyll synthesis. Collectively, the results indicate that NO3--N deficiency affects enzyme activity by altering the expression of key genes in the nitrogen assimilation pathway, thereby suppressing NO3--N absorption and assimilation. NO3--N deficiency inhibits the synthesis of the chlorophyll precursor PBG, thereby hindering chlorophyll synthesis.

Comparison Between Flat and Round Peaches, Genomic Evidences of Heterozygosity Events.

Bud sports occur in many plant species, including fruit trees. Although they are correlated with genetic variance in somatic cells, the mechanisms responsible for bud sports are mostly unknown. In this study, a peach bud sport whose fruit shape was transformed to round from flat was identified by next generation sequencing (NGS), and we provide evidence that a long loss of heterozygosity (LOH) event may be responsible for this alteration in fruit shape. Moreover, compared to the reference genome, we identified 237,476 high quality single nucleotide polymorphisms (SNPs) in the wild-type and bud sport genomes. Using this SNP set, a long LOH event was identified at the distal end of scaffold Pp06 of the bud sport genome. Haplotypes from 155 additional peach accessions were phased, suggesting that the homozygous distal end of scaffold Pp06 of the bud sport was likely derived from only one haplotype of the wild-type flat peach. A genome-wide association study (GWAS) of 127 peach accessions was conducted to associate a SNP found at 26,924,482 bp of scaffold Pp06 to differences in fruit shape. All accessions with round-shaped fruit were found to have an A/A genotype, while those with A/T, or T/T genotypes had flat-shaped fruits. Finally, we also found that 236 peach accessions and 141 Prunus species with round-type fruit were found to have an A/A genotype at this SNP, while 22 flat peach accessions had an A/T genotype. Taken together, our results suggest that genes flanking this A/T polymorphism, and haplotyped carrying the T allele may determine flat fruit shape in this population. Furthermore, the LOH event resulting in the loss of the haplotype carrying the T allele may therefore be responsible for fruit shape alteration in wild-type flat peach.

Transcriptomic and Functional Analyses Reveal That PpGLK1 Regulates Chloroplast Development in Peach (Prunus persica).

Peach is an ideal species for fruit tree research because of its small, fully sequenced genome. Chloroplast development is dependent on the tight cooperation between the nuclear and plastid genomes, and is regulated by GLK transcription factors. In this work, the pigment content was monitored and the chloroplast-to-chromoplast conversion during the fruit ripening was visualized by transmission electron microscopy. Localization and expression analyses showed that PpGLK1 was located in the nucleus and expressed mainly in the leaves and fruit skin. A transcriptome analysis showed that PpGLK1 and its target genes were significantly differentially expressed in ripening peach fruit skin. PpGLK1 silencing affected chlorophyll accumulation in peach leaves and fruits. Overexpression of PpGLK1 rescued the phenotypes of the Arabidopsis Atglk1Atglk2 double mutant and the tomato uniform ripening mutant. The results of a yeast two-hybrid analysis showed that PpGLK1 is autoactivated and that PpGLK1 (301-542 a.a.) interacted with PpARF5. Together, our results indicate that PpGLK1 regulates chloroplast development in green tissues in peach. Therefore, it may be a promising target gene for improving the production and quality of peach by genetic engineering and breeding approaches.