Ca2+-independent ZmCPK2 is inhibited by Ca2+-dependent ZmCPK17 during drought response in maize.

Calcium oscillations are induced by different stresses. Calcium-dependent protein kinases (CDPKs/CPKs) are one major group of the plant calcium decoders that are involved in various processes including drought response. Some CPKs are calcium-independent. Here, we identified ZmCPK2 as a negative regulator of drought resistance by screening an overexpression transgenic maize pool. We found that ZmCPK2 does not bind calcium, and its activity is mainly inhibited during short term abscisic acid (ABA) treatment, and dynamically changed in prolonged treatment. Interestingly, ZmCPK2 interacts with and is inhibited by calcium-dependent ZmCPK17, a positive regulator of drought resistance, which is activated by ABA. ZmCPK17 could prevent the nuclear localization of ZmCPK2 through phosphorylation of ZmCPK2T60. ZmCPK2 interacts with and phosphorylates and activates ZmYAB15, a negative transcriptional factor for drought resistance. Our results suggest that drought stress-induced Ca2+ can be decoded directly by ZmCPK17 that inhibits ZmCPK2, thereby promoting plant adaptation to water deficit.

Acupuncture as Add-on Therapy to SSRIs Can Improve Outcomes of Treatment for Anxious Depression: Subgroup Analysis of the AcuSDep Trial.

Purpose: Anxious depression (AD) is a common, distinct depression subtype. This exploratory subgroup analysis aimed to explore the effects of acupuncture as an add-on therapy of selective serotonin reuptake inhibitors (SSRIs) for patients with AD or non-anxious depression (NAD). Patients and Methods: Four hundred and sixty-five patients with moderate-to-severe depression from the AcuSDep pragmatic trial were included in analysis. Patients were randomly assigned to receive MA+SSRIs, EA+SSRIs, or SSRIs alone (1:1:1) for six weeks. AD was defined by using dimensional criteria. The measurement instruments included 17-items Hamilton Depression Scale (HAMD-17), Self-Rating Depression Scale (SDS), Clinical Global Impression (CGI), Rating Scale for Side Effects (SERS), and WHO Quality of Life-BREF (WHOQOL-BREF). Comparison between AD and NAD subgroups and comparisons between groups within either AD or NAD subgroups were conducted. Results: Eighty percent of the patients met the criteria for AD. The AD subgroup had poorer clinical manifestations and treatment outcomes compared to those of the NAD subgroup. For AD patients, the HAMD response rate, remission rate, early onset rate, and the score changes on each scale at most measurement points on the two acupuncture groups were significantly better than the SSRIs group. For NAD patients, the HAMD early onset rates of the two acupuncture groups were significantly better than the SSRIs group. Conclusion: For AD subtype patients, either MA or EA add-on SSRIs showed comprehensive improvements, with small-to-medium effect sizes. For NAD subtype patients, both the add-on acupuncture could accelerate the response to SSRIs treatment. The study contributed to the existing literature by providing insights into the potential benefits of acupuncture in combination with SSRIs, especially for patients with AD subtypes. Due to its limited nature as a post hoc subgroup analysis, prospectively designed, high-quality trials are warranted. Clinical Trials Registration: ChiCTR-TRC-08000297.

Phosphorylation of ZmAL14 by ZmSnRK2.2 regulates drought resistance through derepressing ZmROP8 expression.

Drought stress has negative effects on crop growth and production. Characterization of transcription factors that regulate the expression of drought-responsive genes is critical for understanding the transcriptional regulatory networks in response to drought, which facilitates the improvement of crop drought tolerance. Here, we identified an Alfin-like (AL) family gene ZmAL14 that negatively regulates drought resistance. Overexpression of ZmAL14 exhibits susceptibility to drought while mutation of ZmAL14 enhances drought resistance. An abscisic acid (ABA)-activated protein kinase ZmSnRK2.2 interacts and phosphorylates ZmAL14 at T38 residue. Knockout of ZmSnRK2.2 gene decreases drought resistance of maize. A dehydration-induced Rho-like small guanosine triphosphatase gene ZmROP8 is directly targeted and repressed by ZmAL14. Phosphorylation of ZmAL14 by ZmSnRK2.2 prevents its binding to the ZmROP8 promoter, thereby releasing the repression of ZmROP8 transcription. Overexpression of ZmROP8 stimulates peroxidase activity and reduces hydrogen peroxide accumulation after drought treatment. Collectively, our study indicates that ZmAL14 is a negative regulator of drought resistance, which can be phosphorylated by ZmSnRK2.2 through the ABA signaling pathway, thus preventing its suppression on ZmROP8 transcription during drought stress response.

Integrative regulatory mechanisms of stomatal movements under changing climate.

Global climate change-caused drought stress, high temperatures and other extreme weather profoundly impact plant growth and development, restricting sustainable crop production. To cope with various environmental stimuli, plants can optimize the opening and closing of stomata to balance CO2 uptake for photosynthesis and water loss from leaves. Guard cells perceive and integrate various signals to adjust stomatal pores through turgor pressure regulation. Molecular mechanisms and signaling networks underlying the stomatal movements in response to environmental stresses have been extensively studied and elucidated. This review focuses on the molecular mechanisms of stomatal movements mediated by abscisic acid, light, CO2 , reactive oxygen species, pathogens, temperature, and other phytohormones. We discussed the significance of elucidating the integrative mechanisms that regulate stomatal movements in helping design smart crops with enhanced water use efficiency and resilience in a climate-changing world.

Reconstitution of phytochrome A-mediated light modulation of the ABA signaling pathways in yeast.

Abscisic acid (ABA), a classical plant hormone, plays an essential role in plant adaptation to environmental stresses. The ABA signaling mechanisms have been extensively investigated, and it was shown that the PYR1 (PYRABACTIN RESISTANCE1)/PYL (PYR1-LIKE)/RCAR (REGULATORY COMPONENT OF ABA RECEPTOR) ABA receptors, the PP2C coreceptors, and the SnRK2 protein kinases constitute the core ABA signaling module responsible for ABA perception and initiation of downstream responses. We recently showed that ABA signaling is modulated by light signals, but the underlying molecular mechanisms remain largely obscure. In this study, we established a system in yeast cells that was not only successful in reconstituting a complete ABA signaling pathway, from hormone perception to ABA-responsive gene expression, but also suitable for functionally characterizing the regulatory roles of additional factors of ABA signaling. Using this system, we analyzed the roles of several light signaling components, including the red and far-red light photoreceptors phytochrome A (phyA) and phyB, and the photomorphogenic central repressor COP1, in the regulation of ABA signaling. Our results showed that both phyA and phyB negatively regulated ABA signaling, whereas COP1 positively regulated ABA signaling in yeast cells. Further analyses showed that photoactivated phyA interacted with the ABA coreceptors ABI1 and ABI2 to decrease their interactions with the ABA receptor PYR1. Together, data from our reconstituted yeast ABA signaling system provide evidence that photoactivated photoreceptors attenuate ABA signaling by directly interacting with the key components of the core ABA signaling module, thus conferring enhanced ABA tolerance to light-grown plants.

Strigolactones promote plant freezing tolerance by releasing the WRKY41-mediated inhibition of CBF/DREB1 expression.

Cold stress is a major abiotic stress that adversely affects plant growth and crop productivity. The C-REPEAT BINDING FACTOR/DRE BINDING FACTOR 1 (CBF/DREB1) transcriptional regulatory cascade plays a key role in regulating cold acclimation and freezing tolerance in Arabidopsis (Arabidopsis thaliana). Here, we show that max (more axillary growth) mutants deficient in strigolactone biosynthesis and signaling display hypersensitivity to freezing stress. Exogenous application of GR245DS , a strigolactone analog, enhances freezing tolerance in wild-type plants and strigolactone-deficient mutants and promotes the cold-induced expression of CBF genes. Biochemical analysis showed that the transcription factor WRKY41 serves as a substrate for the F-box E3 ligase MAX2. WRKY41 directly binds to the W-box in the promoters of CBF genes and represses their expression, negatively regulating cold acclimation and freezing tolerance. MAX2 ubiquitinates WRKY41, thus marking it for cold-induced degradation and thereby alleviating the repression of CBF expression. In addition, SL-mediated degradation of SMXLs also contributes to enhanced plant freezing tolerance by promoting anthocyanin biosynthesis. Taken together, our study reveals the molecular mechanism underlying strigolactones promote the cold stress response in Arabidopsis.

PUB25 and PUB26 dynamically modulate ICE1 stability via differential ubiquitination during cold stress in Arabidopsis.

Ubiquitination modulates protein turnover or activity depending on the number and location of attached ubiquitin (Ub) moieties. Proteins marked by a lysine 48 (K48)-linked polyubiquitin chain are usually targeted to the 26S proteasome for degradation; however, other polyubiquitin chains, such as those attached to K63, usually regulate other protein properties. Here, we show that 2 PLANT U-BOX E3 ligases, PUB25 and PUB26, facilitate both K48- and K63-linked ubiquitination of the transcriptional regulator INDUCER OF C-REPEAT BINDING FACTOR (CBF) EXPRESSION1 (ICE1) during different periods of cold stress in Arabidopsis (Arabidopsis thaliana), thus dynamically modulating ICE1 stability. Moreover, PUB25 and PUB26 attach both K48- and K63-linked Ub chains to MYB15 in response to cold stress. However, the ubiquitination patterns of ICE1 and MYB15 mediated by PUB25 and PUB26 differ, thus modulating their protein stability and abundance during different stages of cold stress. Furthermore, ICE1 interacts with and inhibits the DNA-binding activity of MYB15, resulting in an upregulation of CBF expression. This study unravels a mechanism by which PUB25 and PUB26 add different polyubiquitin chains to ICE1 and MYB15 to modulate their stability, thereby regulating the timing and degree of cold stress responses in plants.

The nitrate transporter NRT2.1 directly antagonizes PIN7-mediated auxin transport for root growth adaptation.

As a crucial nitrogen source, nitrate (NO3-) is a key nutrient for plants. Accordingly, root systems adapt to maximize NO3- availability, a developmental regulation also involving the phytohormone auxin. Nonetheless, the molecular mechanisms underlying this regulation remain poorly understood. Here, we identify low-nitrate-resistant mutant (lonr) in Arabidopsis (Arabidopsis thaliana), whose root growth fails to adapt to low-NO3- conditions. lonr2 is defective in the high-affinity NO3- transporter NRT2.1. lonr2 (nrt2.1) mutants exhibit defects in polar auxin transport, and their low-NO3--induced root phenotype depends on the PIN7 auxin exporter activity. NRT2.1 directly associates with PIN7 and antagonizes PIN7-mediated auxin efflux depending on NO3- levels. These results reveal a mechanism by which NRT2.1 in response to NO3- limitation directly regulates auxin transport activity and, thus, root growth. This adaptive mechanism contributes to the root developmental plasticity to help plants cope with changes in NO3- availability.

Microbiome and metabolic features of tissues and feces reveal diagnostic biomarkers for colorectal cancer.

Microbiome and their metabolites are increasingly being recognized for their role in colorectal cancer (CRC) carcinogenesis. Towards revealing new CRC biomarkers, we compared 16S rRNA gene sequencing and liquid chromatography-mass spectrometry (LC-MS) metabolite analyses in 10 CRC (TCRC) and normal paired tissues (THC) along with 10 matched fecal samples (FCRC) and 10 healthy controls (FHC). The highest microbial phyla abundance from THC and TCRC were Firmicutes, while the dominant phyla from FHC and FCRC were Bacteroidetes, with 72 different microbial genera identified among four groups. No changes in Chao1 indices were detected between tissues or between fecal samples whereas non-metric multidimensional scaling (NMDS) analysis showed distinctive clusters among fecal samples but not tissues. LEfSe analyses indicated Caulobacterales and Brevundimonas were higher in THC than in TCRC, while Burkholderialese, Sutterellaceaed, Tannerellaceaea, and Bacteroidaceae were higher in FHC than in FCRC. Microbial association networks indicated some genera had substantially different correlations. Tissue and fecal analyses indicated lipids and lipid-like molecules were the most abundant metabolites detected in fecal samples. Moreover, partial least squares discriminant analysis (PLS-DA) based on metabolic profiles showed distinct clusters for CRC and normal samples with a total of 102 differential metabolites between THC and TCRC groups and 700 metabolites different between FHC and FCRC groups. However, only Myristic acid was detected amongst all four groups. Highly significant positive correlations were recorded between genus-level microbiome and metabolomics data in tissue and feces. And several metabolites were associated with paired microbes, suggesting a strong microbiota-metabolome coupling, indicating also that part of the CRC metabolomic signature was attributable to microbes. Suggesting utility as potential biomarkers, most such microbiome and metabolites showed directionally consistent changes in CRC patients. Nevertheless, further studies are needed to increase sample sizes towards verifying these findings.

AtMCM10 promotes DNA replication-coupled nucleosome assembly in Arabidopsis.

Minichromosome Maintenance protein 10 (MCM10) is essential for DNA replication initiation and DNA elongation in yeasts and animals. Although the functions of MCM10 in DNA replication and repair have been well documented, the detailed mechanisms for MCM10 in these processes are not well known. Here, we identified AtMCM10 gene through a forward genetic screening for releasing a silenced marker gene. Although plant MCM10 possesses a similar crystal structure as animal MCM10, AtMCM10 is not essential for plant growth or development in Arabidopsis. AtMCM10 can directly bind to histone H3-H4 and promotes nucleosome assembly in vitro. The nucleosome density is decreased in Atmcm10, and most of the nucleosome density decreased regions in Atmcm10 are also regulated by newly synthesized histone chaperone Chromatin Assembly Factor-1 (CAF-1). Loss of both AtMCM10 and CAF-1 is embryo lethal, indicating that AtMCM10 and CAF-1 are indispensable for replication-coupled nucleosome assembly. AtMCM10 interacts with both new and parental histones. Atmcm10 mutants have lower H3.1 abundance and reduced H3K27me1/3 levels with releasing some silenced transposons. We propose that AtMCM10 deposits new and parental histones during nucleosome assembly, maintaining proper epigenetic modifications and genome stability during DNA replication.

Coronatine promotes maize water uptake by directly binding to the aquaporin ZmPIP2;5 and enhancing its activity.

Water uptake is crucial for crop growth and development and drought stress tolerance. The water channel aquaporins (AQP) play important roles in plant water uptake. Here, we discovered that a jasmonic acid analog, coronatine (COR), enhanced maize (Zea mays) root water uptake capacity under artificial water deficiency conditions. COR treatment induced the expression of the AQP gene Plasma membrane intrinsic protein 2;5 (ZmPIP2;5). In vivo and in vitro experiments indicated that COR also directly acts on ZmPIP2;5 to improve water uptake in maize and Xenopus oocytes. The leaf water potential and hydraulic conductivity of roots growing under hyperosmotic conditions were higher in ZmPIP2;5-overexpression lines and lower in the zmpip2;5 knockout mutant, compared to wild-type plants. Based on a comparison between ZmPIP2;5 and other PIP2s, we predicted that COR may bind to the functional site in loop E of ZmPIP2;5. We confirmed this prediction by surface plasmon resonance technology and a microscale thermophoresis assay, and showed that deleting the binding motif greatly reduced COR binding. We identified the N241 residue as the COR-specific binding site, which may activate the channel of the AQP tetramer and increase water transport activity, which may facilitate water uptake under hyperosmotic stress.

Circulating level of homocysteine contributes to diabetic retinopathy associated with dysregulated lipid profile and impaired kidney function in patients with type 2 diabetes mellitus.

BACKGROUND: To test the hypothesis that elevated plasma levels of homocysteine (Hcy) and lipoprotein (a) (LPA) contribute to diabetic retinopathy (DR) associated with dysregulated lipid profile, dyslipidaemia, and kidney function. METHODS: A total of 83 patients with type 2 diabetes mellitus (T2DM) were enrolled in this prospective case-control study. Patients were categorized into those with no DR (DM), non-proliferative DR (NPDR), and proliferative DR (PDR). Age and sex-matched individuals with no diabetes were included in the control group. Biochemical tests, including fasting blood glucose (FBG), glycated hemoglobin (HbA1c), Hcy, LPA, lipid profile, and urine microalbumin (UMA), were evaluated. RESULTS: Hcy was negatively correlated with high-density lipoprotein-cholesterol (HDL-C) (p < 0.05), but positively correlated with [total cholesterol (TC)-HDL-C)/HDL-C] (p < 0.05), low-density lipoprotein cholesterol (LDL-C)/HDL-C (p < 0.05), and UMA (p < 0.05). Traditional risk factors, Hcy, arteriosclerosis-associated plasma indices, and UMA, resulted as the independent risk factors for the occurrence of DM and DR. After controlling for age, sex, duration of DM, and FBG, a multiple ordinal logistic regression model showed that LPA [OR = 2.90, 95% confidence interval (95% CI) 1.16-7.23, p = 0.023)], LDL-C (OR = 4.28, 95% CI 1.24-14.79, p = 0.021), and (TC-HDL-C)/HDL-C (OR = 1.92, 95% CI 1.05-3.53, p = 0.035) were risk factors for DM and DR. CONCLUSIONS: Hcy and LPA contributed to DM and DR. Hcy was positively correlated with kidney dysfunction and the ratios of lipid profiles, and negatively with HDL-C, LPA, LDL-C, and (TC-HDL-C)/HDL-C resulted as predictors of the occurrence of DM and severity of DR.

The clade F PP2C phosphatase ZmPP84 negatively regulates drought tolerance by repressing stomatal closure in maize.

Drought is a major environmental stress that threatens crop production. Therefore, identification of genes involved in drought stress response is of vital importance to decipher the molecular mechanism of stress signal transduction and breed drought tolerance crops, especially for maize. Clade A PP2C phosphatases are core abscisic acid (ABA) signaling components, regulating ABA signal transduction and drought response. However, the roles of other clade PP2Cs in drought resistance remain largely unknown. Here, we discovered a clade F PP2C, ZmPP84, that negatively regulates drought tolerance by screening a transgenic overexpression maize library. Quantitative RT-PCR indicates that the transcription of ZmPP84 is suppressed by drought stress. We identified that ZmMEK1, a member of the MAPKK family, interacts with ZmPP84 by immunoprecipitation and mass spectrometry analysis. Additionally, we found that ZmPP84 can dephosphorylate ZmMEK1 and repress its kinase activity on the downstream substrate kinase ZmSIMK1, while ZmSIMK1 is able to phosphorylate S-type anion channel ZmSLAC1 at S146 and T520 in vitro. Mutations of S146 and T520 to phosphomimetic aspartate could activate ZmSLAC1 currents in Xenopus oocytes. Taken together, our study suggests that ZmPP84 is a negative regulator of drought stress response that inhibits stomatal closure through dephosphorylating ZmMEK1, thereby repressing ZmMEK1-ZmSIMK1 signaling pathway.

Nitrate availability controls translocation of the transcription factor NAC075 for cell-type-specific reprogramming of root growth.

Plant root architecture flexibly adapts to changing nitrate (NO3-) availability in the soil; however, the underlying molecular mechanism of this adaptive development remains under-studied. To explore the regulation of NO3--mediated root growth, we screened for low-nitrate-resistant mutant (lonr) and identified mutants that were defective in the NAC transcription factor NAC075 (lonr1) as being less sensitive to low NO3- in terms of primary root growth. We show that NAC075 is a mobile transcription factor relocating from the root stele tissues to the endodermis based on NO3- availability. Under low-NO3- availability, the kinase CBL-interacting protein kinase 1 (CIPK1) is activated, and it phosphorylates NAC075, restricting its movement from the stele, which leads to the transcriptional regulation of downstream target WRKY53, consequently leading to adapted root architecture. Our work thus identifies an adaptive mechanism involving translocation of transcription factor based on nutrient availability and leading to cell-specific reprogramming of plant root growth.

Active DNA demethylation in plants: 20 years of discovery and beyond.

Maintaining proper DNA methylation levels in the genome requires active demethylation of DNA. However, removing the methyl group from a modified cytosine is chemically difficult and therefore, the underlying mechanism of demethylation had remained unclear for many years. The discovery of the first eukaryotic DNA demethylase, Arabidopsis thaliana REPRESSOR OF SILENCING 1 (ROS1), led to elucidation of the 5-methylcytosine base excision repair mechanism of active DNA demethylation. In the 20 years since ROS1 was discovered, our understanding of this active DNA demethylation pathway, as well as its regulation and biological functions in plants, has greatly expanded. These exciting developments have laid the groundwork for further dissecting the regulatory mechanisms of active DNA demethylation, with potential applications in epigenome editing to facilitate crop breeding and gene therapy.

Natural polymorphism of ZmICE1 contributes to amino acid metabolism that impacts cold tolerance in maize.

Cold stress negatively affects maize (Zea mays L.) growth, development and yield. Metabolic adjustments contribute to the adaptation of maize under cold stress. We show here that the transcription factor INDUCER OF CBF EXPRESSION 1 (ZmICE1) plays a prominent role in reprogramming amino acid metabolome and COLD-RESPONSIVE (COR) genes during cold stress in maize. Derivatives of amino acids glutamate/asparagine (Glu/Asn) induce a burst of mitochondrial reactive oxygen species, which suppress the cold-mediated induction of DEHYDRATION RESPONSE ELEMENT-BINDING PROTEIN 1 (ZmDREB1) genes and impair cold tolerance. ZmICE1 blocks this negative regulation of cold tolerance by directly repressing the expression of the key Glu/Asn biosynthesis genes, ASPARAGINE SYNTHETASEs. Moreover, ZmICE1 directly regulates the expression of DREB1s. Natural variation at the ZmICE1 promoter determines the binding affinity of the transcriptional activator ZmMYB39, a positive regulator of cold tolerance in maize, resulting in different degrees of ZmICE1 transcription and cold tolerance across inbred lines. This study thus unravels a mechanism of cold tolerance in maize and provides potential targets for engineering cold-tolerant varieties.

Natural variations of ZmSRO1d modulate the trade-off between drought resistance and yield by affecting ZmRBOHC-mediated stomatal ROS production in maize.

While crop yields have historically increased, drought resistance has become a major concern in the context of global climate change. The trade-off between crop yield and drought resistance is a common phenomenon; however, the underlying molecular modulators remain undetermined. Through genome-wide association study, we revealed that three non-synonymous variants in a drought-resistant allele of ZmSRO1d-R resulted in plasma membrane localization and enhanced mono-ADP-ribosyltransferase activity of ZmSRO1d toward ZmRBOHC, which increased reactive oxygen species (ROS) levels in guard cells and promoted stomatal closure. ZmSRO1d-R enhanced plant drought resilience and protected grain yields under drought conditions, but it led to yield drag under favorable conditions. In contrast, loss-of-function mutants of ZmRBOHC showed remarkably increased yields under well-watered conditions, whereas they showed compromised drought resistance. Interestingly, by analyzing 189 teosinte accessions, we found that the ZmSRO1d-R allele was present in teosinte but was selected against during maize domestication and modern breeding. Collectively, our work suggests that the allele frequency reduction of ZmSRO1d-R in breeding programs may have compromised maize drought resistance while increased yields. Therefore, introduction of the ZmSRO1d-R allele into modern maize cultivars would contribute to food security under drought stress caused by global climate change.

The transcriptional co-repressor SEED DORMANCY 4-LIKE (AtSDR4L) promotes the embryonic-to-vegetative transition in Arabidopsis thaliana.

Repression of embryonic traits during the seed-to-seedling phase transition requires the inactivation of master transcription factors associated with embryogenesis. How the timing of such inactivation is controlled is unclear. Here, we report on a novel transcriptional co-repressor, Arabidopsis thaliana SDR4L, that forms a feedback inhibition loop with the master transcription factors LEC1 and ABI3 to repress embryonic traits post-imbibition. LEC1 and ABI3 regulate their own expression by inducing AtSDR4L during mid to late embryogenesis. AtSDR4L binds to sites upstream of LEC1 and ABI4, and these transcripts are upregulated in Atsdr4l seedlings. Atsdr4l seedlings phenocopy a LEC1 overexpressor. The embryonic traits of Atsdr4l can be partially rescued by impairing LEC1 or ABI3. The penetrance and expressivity of the Atsdr4l phenotypes depend on both developmental and external cues, demonstrating the importance of AtSDR4L in seedling establishment under suboptimal conditions.

Plasma Apolipoproteins Predicting the Occurrence and Severity of Diabetic Retinopathy in Patients With Type 2 Diabetes Mellitus.

Objective: Apolipoproteins are amphipathic molecules and the major components of plasma lipoproteins. This study aims to investigate the effects of dysregulated apolipoprotein (apo) profiles and their ratios on type 2 diabetes mellitus (T2DM) and diabetic retinopathy (DR) further to test the hypothesis that altered serum level of apolipoproteins is strong biomarkers for DR. Research Design and Methods: This case-control study consists of 157 patients with T2DM including DM without DR, non-proliferative DR (NPDR), and proliferative DR (PDR). Fifty-eight age- and sex-matched healthy subjects were enrolled as normal controls. Blood biochemistry profile including serum levels of glucose, glycated hemoglobin (HbA1c), lipid profile [total cholesterol (TC), Triglycerides (TG), high and low-density lipoprotein (HDL-C and LDL-C)] was estimated. Apolipoproteins (apos, A-I, A-II, B, C-II, C-III, and E) was evaluated by protein chips (Luminex technology). Apolipoprotein ratios and arteriosclerosis-associated plasma indices were calculated. The Kruskal-Wallis test, independent sample t-test or Mann-Whitney U test, and multivariate regression analysis were performed to investigate the association of serum lipid biomarkers and the DR severity. Results: Serum level of apoA-I was negatively correlated with TC-(HDL-C)/HDL-C (p < 0.001), fasting glucose (p < 0.001), HbA1c (p < 0.001), and (p<0.001), while apoE, apoC-II/apoC-III, apoA-II/apoA-I were positively correlated with above traditional biomarkers (p < 0.001). Single variable logistic analysis results showed that body mass index (BMI) (p = 0.023), DM duration (p < 0.001), apoE (p < 0.001), apoC-II/apo C-III (p < 0.001), apoE/apoC-II (p < 0.001), atherogenic index (p = 0.013), fasting glucose (p < 0.001), HbA1c (p < 0.001), LPA (p = 0.001), and LDL-C/HDL-C (p = 0.031) were risk factors for the occurrence and severity of DR. Multivariate logistic regression mode showed that apoC-II/apoC-III and apoB/non-HDL-C (p < 0.001) as well as apoE/apoC-II (p = 0.001) were the independent risk factors for the occurrence and severity of DR-apopA-I and apoA-II are protective factors for DR-after controlling for the duration of DM, HbA1c, fasting glucose, and LPA. Conclusions: apoE, apoC-II/apoC-III, apoE/apoC-II, and apoB/non-HDL-C could be used as novel biomarkers for occurrence and severity of DR, whereas apoA-I and apoA-II resulted as protective factors for DR.