A pattern for the early, middle, and late phase of tea chrysanthemum response to Fusarium oxysporum.

Chrysanthemum morifolium is cultivated worldwide and has high ornamental, tea, and medicinal value. With the increasing area of chrysanthemum cultivation and years of continuous cropping, Fusarium wilt disease frequently occurs in various production areas, seriously affecting the quality and yield and causing huge economic losses. However, the molecular response mechanism of Fusarium wilt infection remains unclear, which limits the molecular breeding process for disease resistance in chrysanthemums. In the present study, we analyzed the molecular response mechanisms of 'Huangju,' one of the tea chrysanthemum cultivars severely infested with Fusarium wilt in the field at the early, middle, and late phases of F. oxysporum infestation. 'Huangju' responded to the infestation mainly through galactose metabolism, plant-pathogen interaction, auxin, abscisic acid, and ethylene signalling in the early phase; galactose metabolism, plant-pathogen interaction, auxin, salicylic acid signal, and certain transcription factors (e.g., CmWRKY48) in the middle phase; and galactose metabolism in the late phase. Notably, the galactose metabolism was important in the early, middle, and late phases of 'Huangju' response to F. oxysporum. Meanwhile, the phytohormone auxin was involved in the early and middle responses. Furthermore, silencing of CmWRKY48 in 'Huangju' resulted in resistance to F. oxysporum. Our results revealed a new molecular pattern for chrysanthemum in response to Fusarium wilt in the early, middle, and late phases, providing a foundation for the molecular breeding of chrysanthemum for disease resistance.

Heterografting enhances chrysanthemums resistance to Alternaria alternata via jasmonate-mediated increases in trichomes and terpenoids.

Trichomes, specialized hair-like structures in the epidermal cells of the aboveground parts of plants, protect plants from pests and pathogens and produce valuable metabolites. Chrysanthemum morifolium, used in tea products, has ornamental and medicinal value. However, it is susceptible to Alternaria alternata fungal infection, posing a threat to its production and use, resulting in substantial economic losses. Increasing the density of glandular trichomes enhances disease resistance and improves the production of medicinal metabolites in chrysanthemums. Jasmonate (JA), promotes the formation of glandular trichomes in various plants. However, it remains unclear whether glandular trichome in chrysanthemums are regulated by JA. Grafting, a technique to improve plant resistance to biotic stresses, has been insufficiently explored in its impact on glandular trichomes, terpenoids, and disease resistance. In this study, we demonstrated that grafting with Artemisia vulgaris rootstocks improves the resistance of chrysanthemum scions to A. alternata. Heterografted chrysanthemums exhibited higher trichome density and terpenoid content compared to self-grafted counterparts. Transcriptome analysis highlighted the significant role of CmJAZ1-like in disease resistance in heterografted chrysanthemums. Overexpressing CmJAZ1-like lines exhibited sensitivity to A. alternate, characterized by reduced glandular trichome density and limited terpenoids. Conversely, silencing lines exhibited resistance to A. alternata showcasing increased glandular trichome density and abundant terpenoids. Higher JA content was confirmed in heterografted chrysanthemum scions compared to self-grafted ones. Furthermore, we established that JA promotes the development of glandular trichomes and the synthesis of terpenoids while inducing the degradation of CmJAZ1-like proteins in chrysanthemums. These findings suggest that higher JA increases trichome density and terpenoid content, enhancing resistance to A. alternata by regulating CmJAZ1-like in heterografted chrysanthemums.

Origami-inspired highly stretchable and breathable 3D wearable sensors for in-situ and online monitoring of plant growth and microclimate.

The emerging wearable plant sensors demonstrate the capability of in-situ measurement of physiological and micro-environmental information of plants. However, the stretchability and breathability of current wearable plant sensors are restricted mainly due to their 2D planar structures, which interfere with plant growth and development. Here, origami-inspired 3D wearable sensors have been developed for plant growth and microclimate monitoring. Unlike 2D counterparts, the 3D sensors demonstrate theoretically infinitely high stretchability and breathability derived from the structure rather than the material. They are adjusted to 100% and 111.55 mg cm-2·h-1 in the optimized design. In addition to stretchability and breathability, the structural parameters are also used to control the strain distribution of the 3D sensors to enhance sensitivity and minimize interference. After integrating with corresponding sensing materials, electrodes, data acquisition and transmission circuits, and a mobile App, a miniaturized sensing system is produced with the capability of in-situ and online monitoring of plant elongation and microclimate. As a demonstration, the 3D sensors are worn on pumpkin leaves, which can accurately monitor the leaf elongation and microclimate with negligible hindrance to plant growth. Finally, the effects of the microclimate on the plant growth is resolved by analyzing the monitored data. This study would significantly promote the development of wearable plant sensors and their applications in the fields of plant phenomics, plant-environment interface, and smart agriculture.

Comparative transcriptome analysis provides molecular insights into heterosis of waterlogging tolerance in Chrysanthemum indicum.

BACKGROUND: Heterosis breeding is one of the most important breeding methods for chrysanthemum. To date, the genetic mechanisms of heterosis for waterlogging tolerance in chrysanthemum are still unclear. This study aims to analyze the expression profiles and potential heterosis-related genes of two hybrid lines and their parents with extreme differences in waterlogging tolerance under control and waterlogging stress conditions by RNA-seq. RESULTS: A population of 140 F1 progeny derived from Chrysanthemum indicum (Nanchang) (waterlogging-tolerant) and Chrysanthemum indicum (Nanjing) (waterlogging-sensitive) was used to characterize the extent of genetic variation in terms of seven waterlogging tolerance-related traits across two years. Lines 98 and 95, respectively displaying positive and negative overdominance heterosis for the waterlogging tolerance traits together with their parents under control and waterlogging stress conditions, were used for RNA-seq. In consequence, the maximal number of differentially expressed genes (DEGs) occurred in line 98. Gene ontology (GO) enrichment analysis revealed multiple stress-related biological processes for the common up-regulated genes. Line 98 had a significant increase in non-additive genes under waterlogging stress, with transgressive up-regulation and paternal-expression dominant patterns being the major gene expression profiles. Further, GO analysis identified 55 and 95 transgressive up-regulation genes that overlapped with the up-regulated genes shared by two parents in terms of responses to stress and stimulus, respectively. 6,640 genes in total displaying maternal-expression dominance patterns were observed in line 95. In addition, 16 key candidate genes, including SAP12, DOX1, and ERF017 which might be of significant importance for the formation of waterlogging tolerance heterosis in line 98, were highlighted. CONCLUSION: The current study provides a comprehensive overview of the root transcriptomes among F1 hybrids and their parents under waterlogging stress. These findings lay the foundation for further studies on molecular mechanisms underlying chrysanthemum heterosis on waterlogging tolerance.

Genetic architecture and genomic prediction of plant height-related traits in chrysanthemum.

Plant height (PH) is a crucial trait determining plant architecture in chrysanthemum. To better understand the genetic basis of PH, we investigated the variations of PH, internode number (IN), internode length (IL), and stem diameter (SD) in a panel of 200 cut chrysanthemum accessions. Based on 330 710 high-quality SNPs generated by genotyping by sequencing, a total of 42 associations were identified via a genome-wide association study (GWAS), and 16 genomic regions covering 2.57 Mb of the whole genome were detected through selective sweep analysis. In addition, two SNPs, Chr1_339370594 and Chr18_230810045, respectively associated with PH and SD, overlapped with the selective sweep regions from FST and π ratios. Moreover, candidate genes involved in hormones, growth, transcriptional regulation, and metabolic processes were highlighted based on the annotation of homologous genes in Arabidopsis and transcriptomes in chrysanthemum. Finally, genomic selection for four PH-related traits was performed using a ridge regression best linear unbiased predictor model (rrBLUP) and six marker sets. The marker set constituting the top 1000 most significant SNPs identified via GWAS showed higher predictabilities for the four PH-related traits, ranging from 0.94 to 0.97. These findings improve our knowledge of the genetic basis of PH and provide valuable markers that could be applied in chrysanthemum genomic selection breeding programs.

Optimum Nitrogen, Phosphorous, and Potassium Fertilizer Application Increased Chrysanthemum Growth and Quality by Reinforcing the Soil Microbial Community and Nutrient Cycling Function.

Nitrogen (N), phosphorus (P), and potassium (K) are three macronutrients that are crucial in plant growth and development. Deficiency or excess of any or all directly decreases crop yield and quality. There is increasing awareness of the importance of rhizosphere microorganisms in plant growth, nutrient transportation, and nutrient uptake. Little is known about the influence of N, P, and K as nutrients for the optimal production of Chrysanthemum morifolium. In this study, a field experiment was performed to investigate the effects of N, P, and K on the growth, nutrient use efficiency, microbial diversity, and composition of C. morifolium. Significant relationships were evident between N application rates, C. morifolium nutrient use, and plant growth. The N distribution in plant locations decreased in the order of leaf > stem > root; the distributions were closely related to rates of N application. Total P fluctuated slightly during growth. No significant differences were found between total P in the roots, stems, and leaves of C. morifolium vegetative organs. Principle component analysis revealed that combinations of N, P, and K influenced soil nutrient properties through their indirect impact on operational taxonomic units, Shannon index, and abundance of predominant bacterial taxa. Treatment with N, P, and K (600, 120, and 80 mg·plant-1, respectively) significantly improved plant growth and quality and contributed to the bacterial richness and diversity more than other concentrations of N, P, and K. At the flowering time, the plant height, leaf fresh weight, root dry weight, stem and leaf dry weight were increased 10.6%, 19.0%, 40.4%, 27% and 34.0%, respectively, when compared to the CK. The optimal concentrations of N, P, and K had a positive indirect influence on the available soil nutrient content and efficiency of nutrient use by plants by increasing the abundance of Proteobacteria, decreasing the abundance of Actinobacteria, and enhancing the potential functions of nitrogen metabolism pathways. N, P, and K fertilization concentrations of 600, 120, and 80 mg·plant-1 were optimal for C. morifolium cultivation, which could change environmental niches and drive the evolution of the soil microbial community and diversity. Shifts in the composition of soil microbes and functional metabolism pathways, such as ABC transporters, nitrogen metabolism, porphyrin, and the metabolism of chlorophyll II, glyoxylate, and dicarboxylate, greatly affected soil nutrient cycling, with potential feedback on C. morifolium nutrient use efficiency and growth. These results provide new insights into the efficient cultivation and management of C. morifolium.

Jasmonate signaling drives defense responses against Alternaria alternata in chrysanthemum.

BACKGROUND: Black spot disease caused by the necrotrophic fungus Alternaria spp. is one of the most devastating diseases affecting Chrysanthemum morifolium. There is currently no effective way to prevent chrysanthemum black spot. RESULTS: We revealed that pre-treatment of chrysanthemum leaves with the methy jasmonate (MeJA) significantly reduces their susceptibility to Alternaria alternata. To understand how MeJA treatment induces resistance, we monitored the dynamics of metabolites and the transcriptome in leaves after MeJA treatment following A. alternata infection. JA signaling affected the resistance of plants to pathogens through cell wall modification, Ca2+ regulation, reactive oxygen species (ROS) regulation, mitogen-activated protein kinase cascade and hormonal signaling processes, and the accumulation of anti-fungal and anti-oxidant metabolites. Furthermore, the expression of genes associated with these functions was verified by reverse transcription quantitative PCR and transgenic assays. CONCLUSION: Our findings indicate that MeJA pre-treatment could be a potential orchestrator of a broad-spectrum defense response that may help establish an ecologically friendly pest control strategy and offer a promising way of priming plants to induce defense responses against A. alternata.

Flowering repressor CmSVP recruits the TOPLESS corepressor to control flowering in chrysanthemum.

Plant flowering time is induced by environmental and endogenous signals perceived by the plant. The MCM1-AGAMOUSDEFICIENS-Serum Response Factor-box (MADS-box) protein SHORT VEGETATIVE PHASE (SVP) is a pivotal repressor that negatively regulates the floral transition during the vegetative phase; however, the transcriptional regulatory mechanism remains poorly understood. Here, we report that CmSVP, a chrysanthemum (Chrysanthemum morifolium Ramat.) homolog of SVP, can repress the expression of a key flowering gene, a chrysanthemum FLOWERING LOCUS T-like gene (CmFTL3), by binding its promoter CArG element to delay flowering in the ambient temperature pathway in chrysanthemum. Protein-protein interaction assays identified an interaction between CmSVP and CmTPL1-2, a chrysanthemum homologue of TOPLESS (TPL) that plays critical roles as transcriptional corepressor in many aspects of plant life. Genetic analyses revealed the CmSVP-CmTPL1-2 transcriptional complex is a prerequisite for CmSVP to act as a floral repressor. Furthermore, overexpression of CmSVP rescued the phenotype of the svp-31 mutant in Arabidopsis (Arabidopsis thaliana), overexpression of AtSVP or CmSVP in the Arabidopsis dominant-negative mutation tpl-1 led to ineffective late flowering, and AtSVP interacted with AtTPL, confirming the conserved function of SVP in chrysanthemum and Arabidopsis. We have validated a conserved machinery wherein SVP partially relies on TPL to inhibit flowering via a thermosensory pathway.

CmWRKY6-1-CmWRKY15-like transcriptional cascade negatively regulates the resistance to fusarium oxysporum infection in Chrysanthemum morifolium.

Chrysanthemum Fusarium wilt is a soil-borne disease that causes serious economic losses to the chrysanthemum industry. However, the molecular mechanism underlying the response of chrysanthemum WRKY to Fusarium oxysporum infection remains largely unknown. In this study, we isolated CmWRKY6-1 from chrysanthemum 'Jinba' and identified it as a transcriptional repressor localized in the nucleus via subcellular localization and transcriptional activation assays. We found that CmWRKY6-1 negatively regulated resistance to F. oxysporum and affected reactive oxygen species (ROS) and salicylic acid (SA) pathways using transgenic experiments and transcriptomic analysis. Moreover, CmWRKY6-1 bound to the W-box element on the CmWRKY15-like promoter and inhibited its expression. Additionally, we observed that CmWRKY15-like silencing in chrysanthemum reduced its resistance to F. oxysporum via transgenic experiments. In conclusion, we revealed the mechanism underlying the CmWRKY6-1-CmWRKY15-like cascade response to F. oxysporum infection in chrysanthemum and demonstrated that CmWRKY6-1 and CmWRKY15-like regulates the immune system.

Biodiversity of Endophytic Microbes in Diverse Tea Chrysanthemum Cultivars and Their Potential Promoting Effects on Plant Growth and Quality.

The endophytic microbiomes significantly differed across tea chrysanthemum cultivars and organs (stems and leaves). The most abundant endophytic bacterial genera were Pseudomonas, Masillia, and Enterobacter in the leaves and Sphingomonas and Curtobacterium in the stems of the five cultivars. Meanwhile, the most abundant endophytic fungal genera in the leaves and stems of the five tea chrysanthemums were Alternaria, Cladosporium, and Sporobolomyces. Specifically, Rhodotorula was dominant in the leaves of 'Jinsi huangjv' and Paraphoma was dominant in the stems of 'Jinsi huangjv'. In all cultivars, the diversity and richness of endophytic bacteria were higher in leaves than in stems (p < 0.05). The highest diversity and richness of endophytic bacteria were recorded in 'Chujv', followed by 'Jinsi huangjv', 'Fubai jv', 'Nannong jinjv', and 'Hangbai jv'. Meanwhile, endophytic fungi were less pronounced. Twenty-seven and 15 cultivable endophytic bacteria and fungi were isolated, four isolated endophytic bacteria, namely, CJY1 (Bacillus oryzaecorticis), CY2 (Pseudomonas psychrotolerans), JSJ7, and JSJ17 (Enterobacter cloacae) showed higher indole acetic acid production ability. Further field studies indicated that inoculation of these four endophytic bacteria not only promoted plant growth and yield but also increased total flavonoids, chlorogenic acid, luteolin, and 3,5-dicoffeylquinic acid levels in the dry flowers of tea chrysanthemums.

Wearable Sensor: An Emerging Data Collection Tool for Plant Phenotyping.

The advancement of plant phenomics by using optical imaging-based phenotyping techniques has markedly improved breeding and crop management. However, there remains a challenge in increasing the spatial resolution and accuracy due to their noncontact measurement mode. Wearable sensors, an emerging data collection tool, present a promising solution to address these challenges. By using a contact measurement mode, wearable sensors enable in-situ monitoring of plant phenotypes and their surrounding environments. Although a few pioneering works have been reported in monitoring plant growth and microclimate, the utilization of wearable sensors in plant phenotyping has yet reach its full potential. This review aims to systematically examine the progress of wearable sensors in monitoring plant phenotypes and the environment from an interdisciplinary perspective, including materials science, signal communication, manufacturing technology, and plant physiology. Additionally, this review discusses the challenges and future directions of wearable sensors in the field of plant phenotyping.

Spin-resolved transport of multifunctional C18molecule-based nanodevices: a first-principles study.

As is well known, Kasieret alfirst synthesized a cyclic molecule C18, as characterized by high-resolution atomic force microscopy, is a polyalkylene structure in which the 18 carbon atoms are linked by alternating single and triple bonds Kaiseret al(2019Science3651299-301). Early studies have found that the C18molecule has semiconducting properties, suggesting that a similar straight-chain carbon structure could become a molecular device. Inspired by this, an analysis of spin-resolved electronic transport of nanodevices made by C18 sandwiched between zigzag graphyne nanoribbon leads or zigzag graphene nanoribbon leads presents here. The computational results demonstrate that a good spin-filtering effect, spin rectifying effect and an obvious negative differential resistance behavior in designed model devices can be obtained. Moreover, a stable dual-spin filtering effect or diode effect can be occurred in considered model devices with leads in an antiparallel state. The intrinsic mechanisms of molecular nanodevices are explained in detail by analyzing the transmission spectrum under different bias voltage, local density of states, molecular projection Hamiltonian, Current-Voltage (I-V) characteristics, transmission pathways,et al. These results are particularly significant for the development of multifunctional spintronic nanodevices.

Potential pathways and genes expressed in Chrysanthemum in response to early fusarium oxysporum infection.

BACKGROUND: Chrysanthemum Fusarium wilt is a common fungal disease caused by Fusarium oxysporum, which causes continuous cropping obstacles and huge losses to the chrysanthemum industry. The defense mechanism of chrysanthemum against F. oxysporum remains unclear, especially during the early stages of the disease. Therefore, in the present study, we analyzed chrysanthemum 'Jinba' samples inoculated with F. oxysporum at 0, 3, and 72 h using RNA-seq. RESULTS: The results revealed that 7985 differentially expressed genes (DEGs) were co-expressed at 3 and 72 h after F. oxysporum infection. We analyzed the identified DEGs using Kyoto Encyclopedia of Genes and Genomes and Gene Ontology. The DEGs were primarily enriched in "Plant pathogen interaction", "MAPK signaling pathway", "Starch and sucrose metabolism", and "Biosynthesis of secondary metabolites". Genes related to the synthesis of secondary metabolites were upregulated in chrysanthemum early during the inoculation period. Furthermore, peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase enzymes were consistently produced to accumulate large amounts of phenolic compounds to resist F. oxysporum infection. Additionally, genes related to the proline metabolic pathway were upregulated, and proline levels accumulated within 72 h, regulating osmotic balance in chrysanthemum. Notably, the soluble sugar content in chrysanthemum decreased early during the inoculation period; we speculate that this is a self-protective mechanism of chrysanthemums for inhibiting fungal reproduction by reducing the sugar content in vivo. In the meantime, we screened for transcription factors that respond to F. oxysporum at an early stage and analyzed the relationship between WRKY and DEGs in the "Plant-pathogen interaction" pathway. We screened a key WRKY as a research target for subsequent experiments. CONCLUSION: This study revealed the relevant physiological responses and gene expression changes in chrysanthemum in response to F. oxysporum infection, and provided a relevant candidate gene pool for subsequent studies on chrysanthemum Fusarium wilt.

Analyses of a chromosome-scale genome assembly reveal the origin and evolution of cultivated chrysanthemum.

Chrysanthemum (Chrysanthemum morifolium Ramat.) is a globally important ornamental plant with great economic, cultural, and symbolic value. However, research on chrysanthemum is challenging due to its complex genetic background. Here, we report a near-complete assembly and annotation for C. morifolium comprising 27 pseudochromosomes (8.15 Gb; scaffold N50 of 303.69 Mb). Comparative and evolutionary analyses reveal a whole-genome triplication (WGT) event shared by Chrysanthemum species approximately 6 million years ago (Mya) and the possible lineage-specific polyploidization of C. morifolium approximately 3 Mya. Multilevel evidence suggests that C. morifolium is likely a segmental allopolyploid. Furthermore, a combination of genomics and transcriptomics approaches demonstrate the C. morifolium genome can be used to identify genes underlying key ornamental traits. Phylogenetic analysis of CmCCD4a traces the flower colour breeding history of cultivated chrysanthemum. Genomic resources generated from this study could help to accelerate chrysanthemum genetic improvement.

CmWRKY41 activates CmHMGR2 and CmFPPS2 to positively regulate sesquiterpenes synthesis in Chrysanthemum morifolium.

Chrysanthemum morifolium is one of the most significant multipurpose crops with ornamental, medicinal, and edible value. Terpenoids, an essentials component of volatile oils, are abundant in chrysanthemum. However, the transcriptional regulation of terpenoid biosynthesis in chrysanthemums remains unclear. In the present investigation, we identified CmWRKY41, whose expression pattern is similar to that of terpenoid content in chrysanthemum floral scent, as a candidate gene that may promote terpenoid biosynthesis in chrysanthemum. Two structural genes 3-hydroxy-3-methylglutaryl-CoA reductase 2 (CmHMGR2) and farnesyl pyrophosphate synthase 2 (CmFPPS2), play key role in terpene biosynthesis in chrysanthemum. CmWRKY41 can directly bind to the promoters of CmHMGR2 or CmFPPS2 through GTGACA or CTGACG elements and activate its expression to promote sesquiterpene biosynthesis. In summary, these results indicate that CmWRKY41 targets CmHMGR2 and CmFPPS2 to positively regulate sesquiterpene biosynthesis in chrysanthemums. This study preliminarily revealed the molecular mechanism of terpenoid biosynthesis in chrysanthemum while enriching the secondary metabolism regulatory network.

Hybrid weakness and continuous flowering caused by compound expression of FTLs in Chrysanthemum morifolium × Leucanthemum paludosum intergeneric hybridization.

Hybridization is an important evolutionary mechanism ubiquitous to plants. Previous studies have shown that hybrid polyploidization of cultivated chrysanthemum, 'Zhongshanzigui', and Leucanthemum paludosum exhibit spring-flowering traits. This study explores the function of the LpFTLs gene via the phenotype of A. thaliana after heterologous transformation of the LpFTLs gene, and analyzes the mechanism ofthe continuous flowering phenotype and heterosis of hybrid offspring. The results suggest that the flowering phenotype of hybrid offspring in spring may be related to the expression of the LpFTLs gene. Ectopic expression of Leucanthemum paludosumLpFTLs in Arabidopsis thaliana resulted in earlier flowering, indicating that the LpFTLs gene also affects the flowering time in L. paludosum. Compound expression of FTLs in C. morifolium × L. paludosum intergeneric hybridization directly leads to serious heterosis in the hybrid offspring. Moreover, continuous flowering appears to be accompanied by hybrid weakness under the balance of vegetative and reproductive growth. Therefore, in future studies on chrysanthemum breeding, a suitable balance point must be established to ensure the target flowering time under normal growth.

Overexpression of CmWRKY8-1-VP64 Fusion Protein Reduces Resistance in Response to Fusarium oxysporum by Modulating the Salicylic Acid Signaling Pathway in Chrysanthemum morifolium.

Chrysanthemum Fusarium wilt, caused by the pathogenic fungus Fusarium oxysporum, severely reduces ornamental quality and yields. WRKY transcription factors are extensively involved in regulating disease resistance pathways in a variety of plants; however, it is unclear how members of this family regulate the defense against Fusarium wilt in chrysanthemums. In this study, we characterized the WRKY family gene CmWRKY8-1 from the chrysanthemum cultivar 'Jinba', which is localized to the nucleus and has no transcriptional activity. We obtained CmWRKY8-1 transgenic chrysanthemum lines overexpressing the CmWRKY8-1-VP64 fusion protein that showed less resistance to F. oxysporum. Compared to Wild Type (WT) lines, CmWRKY8-1 transgenic lines had lower endogenous salicylic acid (SA) content and expressed levels of SA-related genes. RNA-Seq analysis of the WT and CmWRKY8-1-VP64 transgenic lines revealed some differentially expressed genes (DEGs) involved in the SA signaling pathway, such as PAL, AIM1, NPR1, and EDS1. Based on Gene Ontology (GO) enrichment analysis, the SA-associated pathways were enriched. Our results showed that CmWRKY8-1-VP64 transgenic lines reduced the resistance to F. oxysporum by regulating the expression of genes related to the SA signaling pathway. This study demonstrated the role of CmWRKY8-1 in response to F. oxysporum, which provides a basis for revealing the molecular regulatory mechanism of the WRKY response to F. oxysporum infestation in chrysanthemum.

PIN and PILS family genes analyses in Chrysanthemum seticuspe reveal their potential functions in flower bud development and drought stress.

Auxin affects almost all plant growth and developmental processes. The PIN-FORMED (PIN) and PIN-LIKES (PILS) family genes determine the direction and distribution gradient of auxin flow by polar localization on the cell membrane. However, there are no systematic studies on PIN and PILS family genes in chrysanthemum. Here, 18 PIN and 13 PILS genes were identified in Chrysanthemum seticuspe. The evolutionary relationships, physicochemical properties, conserved motifs, cis-acting elements, chromosome localization, collinearity, and expression characteristics of these genes were analyzed. CsPIN10a, CsPIN10b, and CsPIN10c are unique PIN genes in C. seticuspe. Expression pattern analysis showed that these genes had different tissue specificities, and the expression levels of CsPIN8, CsPINS1, CsPILS6, and CsPILS10 were linearly related to the developmental period of the flower buds. In situ hybridization assay showed that CsPIN1a, CsPIN1b, and CsPILS8 were expressed in floret primordia and petal tips, and CsPIN1a was specifically expressed in the middle of the bract primordia, which might regulate lateral expansion of the bracts. CsPIN and CsPILS family genes are also involved in drought stress responses. This study provides theoretical support for the cultivation of new varieties with attractive flower forms and high drought tolerance.

Transcription factor CmbHLH16 regulates petal anthocyanin homeostasis under different lights in Chrysanthemum.

Light is essential to plant survival and elicits a wide range of plant developmental and physiological responses under different light conditions. A low red-to-far red (R/FR) light ratio induces shade-avoidance responses, including decreased anthocyanin accumulation, whereas a high R/FR light ratio promotes anthocyanin biosynthesis. However, the detailed molecular mechanism underpinning how different R/FR light ratios regulate anthocyanin homeostasis remains elusive, especially in non-model species. Here, we demonstrate that a low R/FR light ratio induced the expression of CmMYB4, which suppressed the anthocyanin activator complex CmMYB6-CmbHLH2, leading to the reduction of anthocyanin accumulation in Chrysanthemum (Chrysanthemum morifolium) petals. Specifically, CmMYB4 recruited the corepressor CmTPL (TOPLESS) to directly bind the CmbHLH2 promoter and suppressed its transcription by impairing histone H3 acetylation. Moreover, the low R/FR light ratio inhibited the PHYTOCHROME INTERACTING FACTOR family transcription factor CmbHLH16, which can competitively bind to CmMYB4 and destabilize the CmMYB4-CmTPL protein complex. Under the high R/FR light ratio, CmbHLH16 was upregulated, which impeded the formation of the CmMYB4-CmTPL complex and released the suppression of CmbHLH2, thus promoting anthocyanin accumulation in Chrysanthemum petals. Our findings reveal a mechanism by which different R/FR light ratios fine-tune anthocyanin homeostasis in flower petals.