PAMP-INDUCED SECRETED PEPTIDE 3 modulates salt tolerance through RECEPTOR-LIKE KINASE 7 in plants.

High soil salinity negatively affects plant growth and development, leading to a severe decrease in crop production worldwide. Here, we report that a secreted peptide, PAMP-INDUCED SECRETED PEPTIDE 3 (PIP3), plays an essential role in plant salt tolerance through RECEPTOR-LIKE KINASE 7 (RLK7) in Arabidopsis (Arabidopsis thaliana). The gene encoding the PIP3 precursor, prePIP3, was significantly induced by salt stress. Plants overexpressing prePIP3 exhibited enhanced salt tolerance, whereas a prePIP3 knockout mutant had a salt-sensitive phenotype. PIP3 physically interacted with RLK7, a leucine-rich repeat RLK, and salt stress enhanced PIP3-RLK7 complex formation. Functional analyses revealed that PIP3-mediated salt tolerance is dependent on RLK7. Exogenous application of synthetic PIP3 peptide activated RLK7, and salt treatment significantly induced RLK7 phosphorylation in a PIP3-dependent manner. Notably, MITOGEN-ACTIVATED PROTEIN KINASE3 (MPK3) and MPK6 were downstream of the PIP3-RLK7 module in salt response signaling. Activation of MPK3/6 was attenuated in pip3 or rlk7 mutants under saline conditions. Therefore, MPK3/6 might amplify salt stress response signaling in plants for salt tolerance. Collectively, our work characterized a novel ligand-receptor signaling cascade that modulates plant salt tolerance in Arabidopsis. This study contributes to our understanding of how plants respond to salt stress.

A transcriptional cascade involving BBX22 and HY5 finely regulates both plant height and fruit pigmentation in citrus.

Dwarfing is a pivotal agronomic trait affecting both yield and quality. Citrus species exhibit substantial variation in plant height, among which internode length is a core element. However, the molecular mechanism governing internode elongation remains unclear. Here, we unveiled that the transcriptional cascade consisting of B-BOX DOMAIN PROTEIN 22 (BBX22) and ELONGATED HYPOCOTYL 5 (HY5) finely tunes plant height and internode elongation in citrus. Loss-of-function mutations of BBX22 in an early-flowering citrus (Citrus hindsii "SJG") promoted internode elongation and reduced pigment accumulation, whereas ectopic expression of BBX22 in SJG, sweet orange (C. sinensis), pomelo (C. maxima) or heterologous expression of BBX22 in tomato (Solanum lycopersicum) significantly decreased internode length. Furthermore, exogenous application of gibberellin A3 (GA3) rescued the shortened internode and dwarf phenotype caused by BBX22 overexpression. Additional experiments revealed that BBX22 played a dual role in regulation internode elongation and pigmentation in citrus. On the one hand, it directly bound to and activated the expression of HY5, GA metabolism gene (GA2 OXIDASE 8, GA2ox8), carotenoid biosynthesis gene (PHYTOENE SYNTHASE 1, PSY1) and anthocyanin regulatory gene (Ruby1, a MYB DOMAIN PROTEIN). On the other hand, it acted as a cofactor of HY5, enhancing the ability of HY5 to regulate target genes expression. Together, our results reveal the critical role of the transcriptional cascade consisting of BBX22 and HY5 in controlling internode elongation and pigment accumulation in citrus. Unraveling the crosstalk regulatory mechanism between internode elongation and fruit pigmentation provides key genes for breeding of novel types with both dwarf and health-beneficial fortification in citrus.

Functional study of the soybean stamen-preferentially expressed gene GmFLA22a in regulating male fertility.

China has a high dependence on soybean imports, yield increase at a faster rate is an urgent problem that need to be solved at present. The application of heterosis is one of the effective ways to significantly increase crop yield. In recent years, the development of an intelligent male sterility system based on recessive nuclear sterile genes has provided a potential solution for rapidly harnessing the heterosis in soybean. However, research on male sterility genes in soybean has been lagged behind. Based on transcriptome data of soybean floral organs in our research group, a soybean stamen-preferentially expressed gene GmFLA22a was identified. It encodes a fasciclin-like arabinogalactan protein with the FAS1 domain, and subcellular localization studies revealed that it may play roles in the endoplasmic reticulum. Take advantage of the gene editing technology, the Gmfla22a mutant was generated in this study. However, there was a significant reduction in the seed-setting rate in the mutant plants at the reproductive growth stage. The pollen viability and germination rate of Gmfla22a mutant plants showed no apparent abnormalities. Histological staining demonstrated that the release of pollen grains in the mutant plants was delayed and incomplete, which may due to the locule wall thickening in the anther development. This could be the reason of the reduced seed-setting rate in Gmfla22a mutants. In summary, our study has preliminarily revealed that GmFLA22a may be involved in regulating soybean male fertility. It provides crucial genetic materials for further uncovering its molecular function and gene resources and theoretical basis for the utilization of heterosis in soybean.

Clinical Trial of Losartan for Pulmonary Emphysema: Pulmonary Trials Cooperative Losartan Effects on Emphysema Progression Clinical Trial.

Rationale: There are no pharmacologic agents that modify emphysema progression in patients with chronic obstructive pulmonary disease (COPD). Objectives: To evaluate the efficacy of losartan, an angiotensin receptor blocker, to reduce emphysema progression. Methods: The trial was a multicenter, randomized, placebo-controlled trial conducted between May 2017 and January 2021. Eligible participants were aged ⩾40 years, had moderate to severe airflow obstruction, ⩾10 pack-years of smoking, mild-moderate emphysema on high-resolution computed tomography, and no medical indication for or intolerance of angiotensin receptor blockers. Treatment with losartan 100 mg daily or matching placebo (1:1) was randomly assigned. The primary outcome was emphysema progression on high-resolution computed tomography over 48 weeks. Secondary outcomes included the St George's Respiratory Questionnaire, the modified Medical Research Council dyspnea scale, the COPD Assessment Test, and the Physical Function-Short Form 20a. Measurements and Main Results: A total of 220 participants were enrolled; 58% were men, 19% were African American, and 24% were current smokers. The medians (interquartile ranges) for age were 65 (61-73) years and 48 (36-59) for percent predicted FEV1 after bronchodilator use. The mean (95% confidence interval) percentage emphysema progression was 1.35% (0.67-2.03) in the losartan group versus 0.66% (0.09-1.23) in the placebo group (P = NS). Conclusions: Losartan did not prevent emphysema progression in people with COPD with mild-moderate emphysema. Clinical trial registered with www.clinicaltrials.gov (NCT02696564).

Analysis of Codon Usage Bias in Xyloglucan Endotransglycosylase (XET) Genes.

Xyloglucan endotransglycosylase (XET) genes are widely distributed in most plants, but the codon usage bias of XET genes has remained uncharacterized. Thus, we analyzed the codon usage bias using 4500 codons of 20 XET genes to elucidate the genetic and evolutionary patterns. Phylogenetic and hierarchical cluster analyses revealed that the 20 XET genes belonged to two groups. The closer the genetic distance, the more similar the codon usage preference. The codon usage bias of most XET genes was weak, but there was also some codon usage bias. AGA, AGG, AUC, and GUG were the top four codons (RSCU > 1.5) in the 20 XET genes. CitXET had a stronger codon usage bias, and there were eight optimal codons of CitXET (i.e., AGA, AUU, UCU, CUU, CCA, GCU, GUU, and AAA). The RSCU values underwent a correspondence analysis. The two main factors affecting codon usage bias (i.e., Axes 1 and 2) accounted for 54.8% and 17.6% of the total variation, respectively. Multiple correspondence analysis revealed that XET genes were widely distributed, with Group 1 genes being closer to Axis 1 than Group 2 genes, which were closer to Axis 2. Codons with A/U at the third codon position were distributed closer to Axis 1 than codons with G/C at the third codon position. PgXET, ZmXET, VlXET, VrXET, and PcXET were biased toward codons ending with G/C. In contrast, CitXET, DpXET, and BrpXET were strongly biased toward codons ending with A/U, indicating that these XET genes have a strong codon usage bias. Translational selection and base composition (especially A and U at the third codon position), followed by mutation pressure and natural selection, may be the most important factors affecting codon usage of 20 XET genes. These results may be useful in clarifying the codon usage bias of XET genes and the relevant evolutionary characteristics.

Effects of Exogenous Application of Glycine Betaine Treatment on 'Huangguoggan' Fruit during Postharvest Storage.

Loss of quality in citrus fruit is a common occurrence during postharvest storage due to oxidative stress and energy consumption. In recent years, glycine betaine (GB) has been widely applied to postharvest horticulture fruit. This study aimed to investigate the effect of GB treatment (10 mM and 20 mM) on the quality and antioxidant activity of 'Huangguogan' fruit during postharvest storage at room temperature. Our results indicated that both 10 mM and 20 mM treatments effectively reduced weight and firmness losses and maintained total soluble solid (TSS), titratable acidity (TA), and ascorbic acid contents. Additionally, GB treatment significantly increased the activity of antioxidant enzymes, maintained higher levels of total phenols and total flavonoids, and led to slower accumulation of H2O2. A transcriptome analysis conducted at 28 days after treatment (DAT)identified 391 differentially expressed genes (DEGs) between 20 mM GB (GB-2) and the control (CK) group. These DEGs were enriched in various pathways, particularly related to oxygen oxidoreductase, peroxidase activity, and flavonoid biosynthesis. Overall, the application of GB proved beneficial in enhancing the storability and extending the shelf life of 'Huangguogan' fruit.

TRIPTYCHON-LIKE regulates aspects of both fruit flavor and color in citrus.

Deciphering the genetic basis of organoleptic traits is critical for improving the quality of fruits, which greatly shapes their appeal to consumers. Here, we characterize the citrus R3-MYB transcription factor TRIPTYCHON-LIKE (CitTRL), which is closely associated with the levels of citric acid, proanthocyanidins (PAs), and anthocyanins. Overexpression of CitTRL lowered acidity levels and PA contents in citrus calli as well as anthocyanin and PA contents in Arabidopsis leaves and seeds. CitTRL interacts with the two basic helix-loop-helix (bHLH) proteins CitbHLH1 and ANTHOCYANIN 1 (CitAN1) to regulate fruit quality. We show that CitTRL competes with the R2R3-MYB CitRuby1 for binding to CitbHLH1 or CitAN1, thereby repressing their activation of anthocyanin structural genes. CitTRL also competes with a second R2R3-MYB, CitPH4, for binding to CitAN1, thus altering the expression of the vacuolar proton-pump gene PH5 and Leucoanthocyanidin reductase, responsible for vacuolar acidification and proanthocyanidins biosynthesis, respectively. Moreover, CitPH4 activates CitTRL transcription, thus forming an activator-repressor loop to prevent the overaccumulation of citric acid and PAs. Overall, this study demonstrates that CitTRL acts as a repressor of the accumulation of citric acid, PAs, and anthocyanins by a cross-regulation mechanism. Our results provide an opportunity to simultaneously manipulate these key traits as a means to produce citrus fruits that are both visually and organoleptically appealing.

SUMOylation of MYB30 enhances salt tolerance by elevating alternative respiration via transcriptionally upregulating AOX1a in Arabidopsis.

Salt stress reduces crop growth and productivity globally. Here we report that a R2R3-MYB transcription factor MYB30 participates in salt tolerance in Arabidopsis. MYB30 can be SUMOylated by SIZ1 in response to salt stress and the lysine (K)283 of MYB30 is essential for its SUMOylation. In contrast to wild-type MYB30, the MYB30K283R mutant failed to rescue the salt-sensitive phenotype of the myb30-2 mutant, indicating that SUMOylation of MYB30 is required for the salt-stress response. Through transcriptomic analysis, we identified a MYB30 target, alternative oxidase 1a (AOX1a). MYB30 binds the promoter of AOX1a and upregulates its expression in response to salt stress; however, MYB30K283R cannot bind the promoter of AOX1a. The cyanide (CN)-resistant alternative respiration (Alt) mediated by AOX is significantly reduced in the myb30-2 mutant through the loss of function of MYB30. As a result, the redox homeostasis is disrupted in the myb30-2 mutant compared with that in wild-type seedlings (WT) under salt conditions. The artificial elimination of excess reactive oxygen species partially rescues the salt-sensitive phenotype of the myb30-2 mutant, whereas after the exogenous application of SHAM, an inhibitor of AOXs and Alt respiration, the salt tolerance of Col-0 and the complemented plants decreased to a level similar to that observed in myb30-2. Finally, overexpression of AOX1a in myb30-2 confers WT-like salt tolerance compared with that of the myb30-2 mutant. Taken together, our results revealed a functional link between MYB30 and AOX1a, and indicated that SIZ1-mediated SUMOylation of MYB30 enhances salt tolerance by regulating Alt respiration and cellular redox homeostasis via AOX1a in Arabidopsis.

Protein kinase PpCIPK1 modulates plant salt tolerance in Physcomitrella patens.

KEY MESSAGE: This work demonstrates that PpCIPK1, a putative protein kinase, participates in regulating plant salt tolerance in moss Physcomitrella patens. Calcineurin B-Like protein (CBL)-interacting protein kinases (CIPKs) have been reported to be involved in multiple signaling networks and function in plant growth and stress responses, however, their biological functions in non-seed plants have not been well characterized. In this study, we report that PpCIPK1, a putative protein kinase, participates in regulating plant salt tolerance in moss Physcomitrella patens (P. patens). Phylogenetic analysis revealed that PpCIPK1 shared high similarity with its homologs in higher plants. PpCIPK1 transcription level was induced upon salt stress in P. patens. Using homologous recombination, we constructed PpCIPK1 knockout mutant lines (PpCIPK1 KO). Salt sensitivity analysis showed that independent PpCIPK1 KO plants exhibited severe growth inhibition and developmental deficiency of gametophytes under salt stress condition compared to that of wild-type P. patens (WT). Consistently, ionic homeostasis was disrupted in plants due to PpCIPK1 deletion, and high level of H2O2 was accumulated in PpCIPK1 KO than that in WT. Furthermore, PpCIPK1 functions in regulating photosynthetic activity in response to salt stress. Interestingly, we observed that PpCIPK1 could completely rescue the salt-sensitive phenotype of sos2-1 to WT level in Arabidopsis, indicating that AtSOS2 and PpCIPK1 are functionally conserved. In conclusion, our work provides evidence that PpCIPK1 participates in salt tolerance regulation in P. patens.

SIMP1 modulates salt tolerance by elevating ERAD efficiency through UMP1A-mediated proteasome maturation in plants.

Salt stress significantly induces accumulation of misfolded or unfolded proteins in plants. Endoplasmic reticulum (ER)-associated protein degradation (ERAD) and other degradative machineries function in the degradation of these abnormal proteins, leading to enhanced salt tolerance in plants. Here we characterise that a novel receptor-like kinase, Salt-Induced Malectin-like domain-containing Protein1 (SIMP1), elevates ERAD efficiency during salt stress through UMP1A, a putative proteasome maturation factor in Arabidopsis. SIMP1 loss-of-function caused a salt-hypersensitive phenotype. SIMP1 interacts and phosphorylates UMP1A, and the protein stability of UMP1A is positively regulated by SIMP1. SIMP1 modulates the 26S proteasome maturation possibly through enhancing the recruitment of specific ß subunits of the core catalytic particle to UMP1A. Functionally, the SIMP1-UMP1A module plays a positive role in ERAD efficiency in Arabidopsis. The degradation of misfolded/unfolded proteins was impaired in both simp1 and ump1a mutants during salt stress. Consistently, both simp1 and ump1a plants exhibited reduced ER stress tolerance. Phenotypic analysis revealed that SIMP1 regulates salt tolerance through UMP1A at least in part. Taken together, our work demonstrated that SIMP1 modulates plant salt tolerance by promoting proteasome maturation via UMP1A, therefore mitigating ER stress through enhanced ERAD efficiency under saline conditions.

Safety of decreasing ureteral stent duration following radical cystectomy.

PURPOSE: We aim to assess the safety of decreasing ureteral stenting duration following Radical Cystectomy with Urinary Diversion (RCUD). MATERIALS AND METHODS: We analyzed a prospectively and retrospectively collected dataset for cystectomy patients at our tertiary center. Adult patient who underwent RCUD for malignancy from January 2013 to February 2018 were included. Patients with a history of abdominal/pelvic radiation and continent diversions were excluded. The patient population was divided to late stent removal group (LSR-POD 14) and early stent removal group (ESR-POD5). Our endpoints were total stent duration, 90-day readmission, 90-day total-UTI, 90-day urinary-readmissions, complications and Ureteroenteric Stricture (UES) rates. Statistical methods included t test, Chi-squared test and multivariate logistic regression. RESULTS: One hundred and seventy-eight patients were included in the final analysis after inclusion/exclusion criteria were applied. The LSR (n = 74) and ESR (n = 104) groups were similar in preoperative characteristics except higher intracorporeal ileal conduit formation in ESR. The duration of stenting decreased significantly from approximately 15.5-5 days (P < 0.001). The LSR had higher 90-day overall readmission rates (OR = 2.57, 95% CI 1.19-5.53, P = 0.016) and total-UTIs (OR = 2.36, 95%CI 1.11-5.04, P = 0.026). With a median follow-up of 9.8 months, UES was similar between the two groups. CONCLUSION: Shorter ureteral stent duration is a safe and non-inferior option following RCUD. It allows for stent removal prior to discharge and less outpatient visits. In addition, decreasing stent duration was linked decreased readmissions and total-UTIs without increased risk of UES. However, future studies are needed to establish causality and promote stent duration change.

Cost saving, patient centered algorithm for progenitor cell mobilization for autologous hematopoietic cell transplantation.

Administration of plerixafor with granulocyte-colony stimulating factor (G-CSF) mobilizes CD34+ cells much more effectively than G-CSF alone, but cost generally limits plerixafor use to patients at high risk of insufficient CD34+ cell collection based on low peripheral blood (PB) CD34+ counts following 4 days of G-CSF. We analyzed costs associated with administering plerixafor to patients with higher day 4 CD34+ cell counts to decrease apheresis days and explored the use of a fixed split dose of plerixafor instead of weight-based dosing. We analyzed 235 patients with plasma cell disorders or non-Hodgkin's lymphoma who underwent progenitor cell mobilization and autologous hematopoietic cell transplantation (AHCT) between March 2014 and December 2017. Two hundred ten (89%) received G-CSF plus Plerixafor and 25 (11%) received G-CSF alone. Overall, 180 patients (77%) collected in 1 day, 53 (22%) in 2 days and 2 (1%) in 3 days. Based on our data, we present a probabilistic algorithm to identify patients likely to require more than one day of collection using G-CSF alone. CD34+ cell yield, ANC and platelet recovery were not significantly different between fixed and standard dose plerixafor. Plerixafor enabled collection in 1 day and with estimated savings of $5000, compared to patients who did not receive plerixafor and required collection for three days. While collection and processing costs and patient populations vary among institutions, our results suggest re-evaluation of current algorithms.

Antimicrobial de-escalation in adult hematopoietic cell transplantation recipients with febrile neutropenia of unknown origin.

BACKGROUND: The optimal duration of empiric antimicrobial therapy in febrile neutropenia of unknown origin is unclear. This study evaluated outcomes in autologous and allogeneic hematopoietic cell transplantation recipients with febrile neutropenia of unknown origin who received early de-escalation of broad-spectrum antimicrobials prior to hematopoietic recovery versus those who continued broad-spectrum antimicrobials until hematopoietic recovery. METHODS: A single-center, retrospective study assessed hematopoietic cell transplantation recipients with febrile neutropenia of unknown origin. Patients were categorized into either cohort 1, representing early de-escalation prior to hematopoietic recovery, or cohort 2, representing continuation of broad-spectrum antimicrobials until hematopoietic recovery. RESULTS: A total of 107 patients were included (22.4% in cohort 1 and 77.6% in cohort 2). Most patients (87.5%) in cohort 1 underwent haploidentical hematopoietic cell transplantation, whereas 84.3% of patients in cohort 2 received autologous hematopoietic cell transplantation. There were no significant differences in rates of recurrent fever (4.2% versus 7.2%, in cohorts 1 and 2, respectively, adjusted odds ratio = 0.84, P = 0.85), re-escalation (4.2% versus 4.8%, adjusted odds ratio = 1.57, P = 0.64), and Clostridioides difficile-associated infections (4.2% versus 2.4%, adjusted odds ratio = 2.27, P = 0.43). No patient experienced in-hospital mortality, intensive care unit admission, or bacteremia. CONCLUSION: Hematopoietic cell transplantation recipients with febrile neutropenia of unknown origin in which broad-spectrum antimicrobials were de-escalated prior to hematopoietic recovery did not experience adverse outcomes. These results concur with recently published studies and the Fourth European Conference on Infections in Leukemia guidelines. An early de-escalation approach in haploidentical hematopoietic cell transplantation recipients specifically appears safe and may result in a reduction in antimicrobial utilization.

Higher Incidence of Hemorrhagic Cystitis Following Haploidentical Related Donor Transplantation Compared with Matched Related Donor Transplantation.

Hemorrhagic cystitis (HC) is a common and important complication of allogeneic hematopoietic cell transplantation (HCT). Reactivation of BK virus is its most common cause. The more intense immunosuppressive regimens administered to recipients of grafts from alternative donors have been reported to account for the increased susceptibility to HC in this population. This study compares patients undergoing HCT with either a haploidentical donor or a matched related donor, all of whom received identical immunosuppression with a post-transplantation cyclophosphamide-based regimen. The incidence of HC was significantly higher in the patients receiving a haploidentical graft (P = .01). The higher incidence of HC in haploidentical graft recipients is therefore directly related to the inherent immune deficiency that follows HLA-mismatched transplantation, independent of the intensity of pharmacologic immunosuppression. This finding carries significant clinical impact for the prevention and treatment of HC in haploidentical graft recipients.

Patellin1 Negatively Modulates Salt Tolerance by Regulating PM Na+/H+ Antiport Activity and Cellular Redox Homeostasis in Arabidopsis.

Soil salinity significantly represses plant development and growth. Mechanisms involved sodium (Na+) extrusion and compartmentation, intracellular membrane trafficking as well as redox homeostasis regulation play important roles in plant salt tolerance. In this study, we report that Patellin1 (PATL1), a membrane trafficking-related protein, modulates salt tolerance in Arabidopsis. The T-DNA insertion mutant of PATL1 (patl1) with an elevated PATL1 transcription level displays a salt-sensitive phenotype. PATL1 partially associates with the plasma membrane (PM) and endosomal system, and might participate in regulating membrane trafficking. Interestingly, PATL1 interacts with SOS1, a PM Na+/H+ antiporter in the Salt-Overly-Sensitive (SOS) pathway, and the PM Na+/H+ antiport activity is lower in patl1 than in Col-0. Furthermore, the reactive oxygen species (ROS) content is higher in patl1 and the redox signaling of antioxidants is partially disrupted in patl1 under salt stress conditions. Artificial elimination of ROS could partially rescue the salt-sensitive phenotype of patl1. Taken together, our results indicate that PATL1 participates in plant salt tolerance by regulating Na+ transport at least in part via SOS1, and by modulating cellular redox homeostasis during salt stress.

RHA2b-mediated MYB30 degradation facilitates MYB75-regulated, sucrose-induced anthocyanin biosynthesis in Arabidopsis seedlings.

Anthocyanins play diverse roles in plant physiology and stress adaptation. In Arabidopsis, the MYB-bHLH-WD40 (MBW) complex has a crucial role in the regulation of anthocyanin synthesis. Here, we report that the R2R3-MYB transcription factor MYB30 and the ubiquitin E3 ligase RHA2b participate in anthocyanin biosynthesis through regulation of the MBW complex. MYB30 was found to negatively regulate sucrose-induced anthocyanin biosynthesis in Arabidopsis seedlings. Expression of multiple genes involved in flavonoid or anthocyanin biosynthesis was affected in the myb30 mutant, and MYB30 directly repressed the expression of MYB75, which encodes a core component of the MBW complex, by binding to its promoter. Moreover, MYB30 physically interacted with MYB75 to inhibit its activity by repressing MBW complex assembly. In addition, sucrose treatment significantly promoted MYB30 degradation via the action of RHA2b. The ubiquitination and degradation of MYB30 were significantly attenuated in the rha2b mutant under high-sucrose treatment, and further analysis showed that MYB75 directly promoted RHA2b expression in response to high sucrose. Our work thus reveals an anthocyanin biosynthetic regulatory module, RHA2b-MYB30, that controls the function of the MBW complex via MYB75. The repression of MYB75 by MYB30 is released by MYB75-induced RHA2b expression, thus ensuring the self-activation of MYB75 when anthocyanin synthesis is needed.

Genome-Wide Analysis of the GLK Gene Family and Its Expression at Different Leaf Ages in the Citrus Cultivar Kanpei.

The GLK gene family plays a crucial role in the regulation of chloroplast development and participates in chlorophyll synthesis. However, the precise mechanism by which GLK contributes to citrus's chlorophyll synthesis remains elusive. The GLK gene family causes variations in the photosynthetic capacity and chlorophyll synthesis of different citrus varieties. In this study, we identified tissue-specific members and the key CcGLKs involved in chlorophyll synthesis. A total of thirty CcGLK transcription factors (TFs) were discovered in the citrus genome, distributed across all nine chromosomes. The low occurrence of gene tandem duplication events and intronic variability suggests that intronic variation may be the primary mode of evolution for CcGLK TFs. Tissue-specific expression patterns were observed for various GLK family members; for instance, CcGLK12 and CcGLK15 were specifically expressed in the skin, while CcGLK30 was specific to the ovary, and CcGLK10, CcGLK6, CcGLK21, CcGLK2, CcGLK18, CcGLK9, CcGLK28, and CcGLK8 were specifically expressed in the leaves. CcGLK4, CcGLK5, CcGLK11, CcGLK23, CcGLKl7, CcGLK26, and CcGLK20 may participate in the regulation of the ALA, prochlorophylate, protoporphyrin IX, Mg-protoporphyrin IX, Chl b, T-Chl, MG-ProtoIX ME, and POR contents in citrus.

Analysis of sugar components and identification of SPS genes in citrus fruit development.

Sugar is a primary determinant of citrus fruit flavour, but undergoes varied accumulation processes across different citrus varieties owing to high genetic variability. Sucrose phosphate synthase (SPS), a key enzyme in glucose metabolism, plays a crucial role in this context. Despite its significance, there is limited research on sugar component quality and the expression and regulatory prediction of SPS genes during citrus fruit development. Therefore, we analysed the sugar quality formation process in 'Kiyomi' and 'Succosa', two citrus varieties, and performed a comprehensive genome-wide analysis of citrus CsSPSs. We observed that the accumulation of sugar components significantly differs between the two varieties, with the identification of four CsSPSs in citrus. CsSPS sequences were highly conserved, featuring typical SPS protein domains. Expression analysis revealed a positive correlation between CsSPS expression and sugar accumulation in citrus fruits. However, CsSPS expression displays specificity to different citrus tissues and varieties. Transcriptome co-expression network analysis suggests the involvement of multiple transcription factors in shaping citrus fruit sugar quality through the regulation of CsSPSs. Notably, the expression levels of four CsWRKYs (CsWRKY2, CsWRKY20, CsWRKY28, CsWRKY32), were significantly positively correlated with CsSPSs and CsWRKY20 might can activate sugar accumulation in citrus fruit through CsSPS2. Collectively, we further emphasize the potential importance of CsWRKYs in citrus sugar metabolism, our findings serve as a reference for understanding sugar component formation and predicting CsSPS expression and regulation during citrus fruit development.

Effect of exogenous melatonin on antioxidant properties and fruit softening of 'Fengtang' plum fruit (Prunus salicina Lindl.) during storage at room temperature.

'Fengtang' plums soften quickly and lose flavor after harvest. This study comprehensively evaluated the effect of exogenous melatonin on the fruit quality of 'Fengtang' plums. According to our findings, exogenous melatonin prevented plum fruit from losing water, delayed the decline in firmness, and preserved a high TSS/TA level. Additionally, exogenous melatonin also enhanced the activity of antioxidant enzymes and increased the non-enzymatic antioxidants, thereby further increasing the antioxidant capacity of plum fruit. Notably, exogenous melatonin delayed the degradation of covalent soluble pectin (CSP), cellulose, and hemicellulose, as well as the rise in water-soluble pectin (WSP) concentration and the activity of cell wall degrading enzymes. Further investigation using atomic force microscopy (AFM) revealed that the chain-like structure of ionic-soluble pectin (ISP) and the self-assembly network structures of CSP were depolymerized, and melatonin treatment retarded the depolymerization of pectin structures. Our results showed that exogenous melatonin preserved the postharvest quality of plum fruits by controlling fruit softness and antioxidant capacity during storage.