Search

Abstract Red leaves in autumn are characteristic of a very early-maturing ripening variety of peach (Prunus persica). Analysis of the genetic factors and molecular mechanisms associated with the red-leaf phenotype can help breed peach very early maturing peach varieties. This study investigated the mechanisms underlying the red- and green-leaf phenotypes in autumn. Red compounds accumulated in the older but not younger leaves in the extremely early-maturing peach variety, ‘99-30-33’, and the leaves of the medium-maturing variety, ‘Zhongtao5 (CP5)’. Metabolic analysis showed that cyanidin-3-O-glucoside was the most abundant anthocyanin in the red leaves. The segregation of the progenies obtained from crossing revealed that the red leaves are a unique hereditary phenomenon not in line with Mendel’s law. BSA-seq and RNA-seq analyses suggest that PpNAC1 was essential for enhancing anthocyanin biosynthesis and was highly upregulated in red than in green leaves. Similar to PpNAC1, the anthocyanin activator, PpMYB10.1, was the only gene highly expressed in red leaves. Moreover, the functional genes involved in anthocyanin biosynthesis, such as Prunus persica Flavonoid 3'-hydroxylase (PpF3'H), Prunus persicaDihydroflavonol reductase (PpDFR), Prunus persica Leucoantho-cyanidin dioxygenase (Pp LDOX), Prunus persica Glutathione S-transferase (PpGST), and Prunus persica UDP-glucose, flavonoid-3-O-glucosyltransferase (PpUFGT), were upregulated in the older red leaves of 99-30-33 but downregulated in the younger 99-30-33 and green CP5 leaves. Yeast one-hybrid and dual-luciferase assays further confirmed that PpNAC1, which refers to 'Prunus persica NAC (NAM、A TAF1/2、CUC1/2)' bound to the promoter of PpMYB10.1, PpMYB10.1 stands for 'Prunus persica MYB (v-myb avian myeloblastosis viral) 10.1' and activated its expression along with those of PpGST and PpUFGT. These results provide insights into the mechanisms responsible for the development of red color in peach leaves in autumn.

Mealy peaches are dry and flavorless, which reduces their consumer acceptance. A deeper understanding of the mechanism underlying mealiness is crucial to enhancing peach fruit quality. In this study, comparative profiling was conducted on CP13, CP14, CM, and RM peaches. Sensory evaluation indicated that CP13 and CM are non-mealy clingstone and freestone peaches, respectively, and CP14 and RM are mealy freestone peaches. Both CP13 and CP14, identified as stony hard (SH) peaches, exhibited minimal ethylene release, whereas CM and RM, identified as melting flesh (MF) peaches, released high amounts of ethylene during the ripening process. Scanning electron microscopy (SEM) microstructure observation indicated that cells in the flesh tissue of mealy peaches, CP14 (SH) and RM (MF), were intact and separated, with large intercellular spaces and irregular arrangements. The main factor that promotes mealiness is differences in pectin metabolism, which impact cell wall composition. The fluctuations in polygalacturonase (PG) and pectin methylesterase (PME) activity between mealy and non-mealy peaches were the main factor contributing to mealiness. However, the changes in cell wall metabolism that caused these fluctuations did not have a clear direction. Using transcriptome analysis and weighted gene co-expression network analysis (WGCNA), we were able to identify forty differentially expressed genes (DEGs) that are associated with mealy patterns. Among these DEGs, genes encoding PG were significantly upregulated in mealy peaches (CP14 and RM) compared to non-mealy peaches (CP13 and CM). PpPG1 was the main effector gene for mealiness, while PpPG2, PpEGase2, PpEXP1, PpEXP3, PpAGP2, PpIAA4, and PpABA2 were identified as candidate genes regulating peach mealiness. These findings provide a solid experimental basis for understanding the textual distinctions between mealy and non-mealy peaches.

Flat peach [Prunus persica (L.) Batsch var. platycarpa] is a variant of ordinary peach with a unique flat shape. It is well known for its shape and delicious fruits (Miao et al. 2022). Although flat peach has a long history of cultivation in China, until the beginning of the 20th century, flat peach was only distributed as a minor variety in the main peach-producing areas of China. In terms of flat peach cultivars, only 46 of the 709 peach cultivars listed in Peach Genetic Resource in China (Wang et al. 2012) are flat peach cultivars, and most of them are flat landraces. Several problems have been noted previously in flat peach cultivars, including poor closure of the blossom end (blossom-end scarring in mild cases and cracking in severe cases), cracked stone in some cultivars (loss of commercial value in severe cases), nonsymmetrical fruit shape, small flesh, and low yield (Wang 2021). Many of the shortcomings of flat peach cultivars are intrinsic problems of the cultivars, which are difficult to improve through cultivation measures. This is the key factor limiting the large-scale promotion of flat peach cultivation in China. For many years, peach breeders in China have been devoted to the genetic improvement of flat peach, and some improved flat peach cultivars have been released, for instance, ‘Pocket Zaoban’ (Jiang et al. 2007) and ‘124 Pantao’ (Ma et al. 2003). However, problems persist in these cultivars, including small fruits, soft flesh, and blossom-end cracks. Only a few flat peach cultivars have good overall performance. In recent years, the Zhengzhou Fruit Research Institute (ZFRI), Chinese Academy of Agricultural Sciences (CAAS), identified genetic sources of flat peach with slow or nonmelting flesh, a well-closed blossom end, and little or no cracking. They were hybridized with high-quality peach and nectarine cultivars or selections. After multiple generations of improvement, breakthroughs were made in early flat peach breeding, and a series of flat peach cultivars with excellent comprehensive traits have been produced. These cultivars are favored by fruit farmers in the main peach-producing areas in China. Hence, the main problems in flat peach cultivation are expected to be solved, which will help expand the cultivation area of flat peach. ‘ZhongPan 101’ and ‘ZhongPan 102’ are two yellow-flesh flat peach cultivars 45 released from the ZFRI, CAAS. These two cultivars produce large, well-shaped, high-quality fruits with a completely closed stylar end and high yield. Three years of evaluation has confirmed that the peach trees of the two cultivars are stable. ‘ZhongPan 101’ and ‘ZhongPan 102’ were well adapted to climate of the middle and lower reaches of the Yellow River; have performed well in Henan, Jiangsu, and Anhui Provinces; and are suggested for trial wherever ‘ZhongYouPan 9’ is grown.

Abstract Background Fruit tree yield and fruit quality are affected by the tree’s growth type, and branching angle is an important agronomic trait of fruit trees, which largely determines the crown structure. The weeping type of peach tree shows good ventilation and light transmission; therefore, it is commonly cultivated. However, there is no molecular marker closely linked with peach weeping traits for target gene screening and assisted breeding. Results First, we confirmed that the peach weeping trait is a recessive trait controlled by a single gene by constructing segregating populations. Based on BSA-seq, we mapped the gene controlling this trait within 159 kb of physical distance on chromosome 3. We found a 35 bp deletion in the candidate area in standard type, which was not lacking in weeping type. For histological assessments, different types of branches were sliced and examined, showing fiber bundles in the secondary xylem of ordinary branches but not in weeping branches. Conclusions This study established a molecular marker that is firmly linked to weeping trait. This marker can be used for the selection of parents in the breeding process and the early screening of hybrid offspring to shorten the breeding cycle. Moreover, we preliminary explored histological differences between growth types. These results lay the groundwork for a better understanding of the weeping growth habit of peach trees.

The storage of peach fruits at 4–5 °C can easily lead to chilling injury and greatly reduce the quality and commercial value of peach fruits. In this study, two kinds of peach fruits (CX and CM) were selected to analyze the mechanisms of chilling injury in fruits with different chilling sensitivity by means of their lipidomic, transcriptome, and dynamic changes in plant hormones. We found that the ethylene, abscisic acid (ABA), and lipid contents changed differently between CX and CM. The ABA and dilactosyl diacylglycerol (DGDG) contents significantly increased after refrigeration in CM fruit, leading to strong cold resistance. However, low temperatures induced a greater accumulation of ethylene, phospholipids, and ABA-GE in CX fruit than in CM fruit, eventually leading to more severe CI symptoms in CX fruit. Additionally, a transcriptional regulatory network for CM and CX fruits during cold storage was constructed, providing a new theoretical reference for the cultivation of cold-resistant peach cultivars and the development of postharvest preservation technology.

IntroductionThe extracellular deposition of β-amyloid (Aβ) is a pathological hallmark in Alzheimer's disease (AD), which induces microglial activation in the pathology of AD. The expression of serine/threonine-protein kinase 2 (SRPK2) is increased in the brain tissues of patients with AD. In this study, we examined the effect of SRPK2 in the activation of microglia.MethodsMicroglia (BV2) cells were cultured and the expression of SRPK2 was enhanced by transfection of SRPK2 recombinant vectors or knockdown by SRPK2 small interfering RNA (siRNA). The cells were stimulated by lipopolysaccharide (LPS) + interferon-γ (IFN-γ) or Aβ in vitro, generating inflammatory cytokines [tumor necrosis factor-α (TNF-α), interleukin (IL)-10, and IL-6], which were investigated by real-time quantitative PCR (qPCR) and ELISA. The proliferation ability of the BV2 cells with/without SRPK2 expression was evaluated by WST-1 under pressure in the presence of Aβ. The effects of SRPK2 on microglia polarization were evaluated by investigating the expression of CD16/32 and CD206 by western blot and the expression of ionized calcium-binding adapter molecule-1 (IBA-1) and arginase-1 (Arg-1) by immunofluorescence. Hippocampal cells HT-22 were cultured with a BV2 cell (with/without SRPK2 expression)-derived medium stimulated by Aβ or LPS + IFN-γ, prior to the evaluation of HT-22 cytotoxicity by assessment of cell viability. Possible relationships between Akt and SRPK2 in the BV2 cells were investigated by western blot.ResultsThe expression of SRPK2 was related to the phenotype polarization changes of microglia with increased expression of CD16/32 and IBA-1. The expression of proinflammatory cytokines IL-6 and TNF-α was increased, whereas the expression of anti-inflammatory cytokine IL-10 was decreased in the BV2 cells with SRPK2 overexpression. Moreover, with the expression enhancement of SRPK2, the BV2 cells had a higher proliferation rate. Aβ treatment can promote SRPK2 expression in BV2 cells. Aβ or LPS + IFN-γ promoted the production of cytokines IL-6 and TNF-α but decreased cytokine IL-10 in the BV2 cells. SRPK2 deficiency alleviated the cytotoxic effects of Aβ or LPS + IFN-γ exposed microglia on HT22 cells. In addition, the activated Akt pathway promoted the expression of SRPK2 in the BV2 cells.ConclusionOur data have found that enhanced SRPK2 expression contributed to the proinflammatory activation of microglia. Thus, SRPK2 may be a key modulating pathway of inflammatory mediators in AD pathology.