Sunflower Gene Research Articles

Comprehensive identification of GASA genes in sunflower and expression profiling in response to drought

Drought stress poses a critical threat to global crop yields and sustainable agriculture. The GASA genes are recognized for their pivotal role in stress tolerance and plant growth, but little is known about how they function in sunflowers. The investigation aimed to identify and elucidate the role of HaGASA genes in conferring sunflowers with drought tolerance. Twenty-seven different HaGASA gene family members were found in this study that were inconsistently located across eleven sunflower chromosomes. Phylogeny analysis revealed that the sunflower HaGASA genes were divided into five subgroups by comparing GASA genes with those from Arabidopsis, peanut, and soybean, with members within each subgroup displaying similar conserved motifs and gene structures. In-silico evaluation of cis-regulatory elements indicated the existence of specific elements associated with stress-responsiveness being the most abundant, followed by hormone, light, and growth-responsive elements. Transcriptomic data from the NCBI database was utilized to assess the HaGASA genes expression profile in different sunflower varieties under drought conditions. The HaGASA genes expression across ten sunflower genotypes under drought stress, revealed 14 differentially expressed HaGASA genes, implying their active role in the plant’s stress response. The expression in different organs revealed that HaGASA2, HaGASA11, HaGASA17, HaGASA19, HaGASA21 and HaGASA26 displayed maximum expression in the stem. Our findings implicate HaGASA genes in mediating sunflower growth maintenance and adaptation to abiotic stress, particularly drought. The findings, taken together, provided a basic understanding of the structure and potential functions of HaGASA genes, setting the framework for further functional investigations into their roles in drought stress mitigation and crop improvement strategies.

Development of a Whole-Cell System Based on the Use of Genetically Modified Protoplasts to Detect Nickel Ions in Food Matrices.

Heavy metals are dangerous contaminants that constitute a threat to human health because they persist in soils and are easily transferred into the food chain, causing damage to human health. Among heavy metals, nickel appears to be one of the most dangerous, being responsible for different disorders. Public health protection requires nickel detection in the environment and food chains. Biosensors represent simple, rapid, and sensitive methods for detecting nickel contamination. In this paper, we report on the setting up a whole-cell-based system, in which protoplasts, obtained from Nicotiana tabacum leaves, were used as transducers to detect the presence of heavy metal ions and, in particular, nickel ions. Protoplasts were genetically modified with a plasmid containing the Green Fluorescent Protein reporter gene (GFP) under control of the promoter region of a sunflower gene coding for a small Heat Shock Protein (HSP). Using this device, the presence of heavy metal ions was detected. Thus, the possibility of using this whole-cell system as a novel tool to detect the presence of nickel ions in food matrices was assessed.

Drought-tolerant transgenic wheat HB4®: a hope for the future

Drought-tolerant transgenic [genetically modified (GM)] HB4® wheat carrying the drought-responsive sunflower gene Hahb4 was first developed in Argentina in 2019 and has already been approved for marketing and consumption as food/feed in at least ten countries. It has also been approved in Argentina and Brazil for commercial cultivation.

Storability, longevity and rancidity: A genomic perspective on evolutionary constraints in major oilseeds

Limited longevity and accelerated chemical decomposition during storage are major problems found in oilseeds. In the present study the genomic composition of rancidity prone soybean and sunflower are compared with oil seeds with fairly good storability like sesame and olive. The chromosomal location, gene duplications, syntenic relationships, cis-element architecture and protein-protein interactions were studied with respect to 250 genes affecting lipid decomposition like lipases, lipoxygenases and oleosins. The expansion of lipoxygenases and phospholipaseD genes in soybean and sunflower indicate the importance of gene duplication in functional divergence. Moreover the effect of strong purifying selection in lipid decomposition genes was evident in shaping the genomic diversity.

Registration of HA‐R20 and HA‐R21 confection sunflower germplasms resistant to rust and downy mildew

AbstractRust and downy mildew (DM) are detrimental diseases in global sunflower (Helianthus annuus L.) production. Disease often results in yield loss and reduced seed quality. Host resistance to DM and rust is mediated by single dominant genes in sunflower. To better utilize genetic resistance, gene pyramiding is a common practice in crop breeding to extend the durability and longevity of resistance. Two confection sunflower germplasm lines, HA‐R20 (Reg. no. GP‐387, PI 702361) and HA‐R21 (Reg. no. GP‐388, PI 702362), were developed using the pedigree breeding method and DNA marker‐assisted selection and released by the USDA‐ARS Sunflower and Plant Biology Research Unit in collaboration with the North Dakota Agricultural Experiment Station in September 2022. HA‐R20 is an F3‐derived F4 confection restorer selection from the cross of HA‐DM2 and HA‐R8, carrying rust resistance genes R12 and R15 and DM resistance gene PlArg. HA‐R21 is an F3‐derived F4 confection maintainer selection from the cross of HA‐DM3 and HA‐R8, carrying rust resistance genes R13a and R15 and DM resistance gene Pl17. Disease reaction and marker testing for DM and rust confirmed that both germplasms harbor DM and rust R genes in the homozygous condition and are resistant to all DM and rust races identified in North America to date. These multiple disease‐resistant lines will provide the sunflower industry with durable disease‐resistant sources for the continued improvement of the crop.

Genome-wide exploration of bZIP transcription factors and their contribution to alkali stress response in Helianthus annuus

The basic leucine zipper (bZIP) gene family is one of the largest transcription factors family in plants. These are involved in various biological processes including the regulation of light signaling, seed maturation, flower development, and the response to both biotic and abiotic stresses. Despite the crucial role of this gene family, no comprehensive investigation has been carried out to characterize bZIPs in sunflower. Therefore, an in silico analysis along with a wetlab experimental approach was adopted for bZIPs in sunflower plants. During the study, 73 bZIPs were identified in sunflower. Phylogenetic analysis involving bZIPs from A. thaliana, H. annuus, C. arabica, L. sativa, and V. vinifera divided these members into 11 groups and testified using conserved motif and gene structure analysis. Protein-Protein interaction analysis identified five clusters of HabZIPs. Intron diversity ranged from 0 to 12. The cis-regulatory elements analysis predicted various stress-responsive elements. RNA-seq data analysis reveiled that clusters of bZIPs were involved in stress response in roots and leaves during early or late stages of plant growth. Similatly, qRT-PCR analysis identified that HabZIP01, 04, 18, and 48 were significantly upregulated in response to mild or svere salt stress. Conversely, HabZIP08 was downregulated in response to both levels of salinity. Overall the study provides new insights into stress-responsive HabZIP genes in sunflower and provides a foundation for further research on their role in the plant's response to abiotic stress.

Evolutionary analysis of the OSCA gene family in sunflower (Helianthus annuus L) and expression analysis under NaCl stress.

Hyperosmolality-gated calcium-permeable channels (OSCA) are Ca2+ nonselective cation channels that contain the calcium-dependent DUF221 domain, which plays an important role in plant response to stress and growth. However, the OSCA gene has not been fully identified and analyzed in sunflowers. In this study, we comprehensively analyzed the number, structure, collinearity, and phylogeny of the OSCA gene family in the sunflower, six Compositae species (Arctium lappa, Chrysanthemum morifolium, Cichorium endivia, Cichorium intybus, Lactuca sativa var. Angustata, and Carthamus tinctorius), and six other plants (soybean, Arabidopsis thaliana, rice, grape, and maize). The expression of the sunflower OSCA gene in nine different tissues, six different hormones, and NaCl stress conditions were analyzed based on transcriptome data and qRT-PCR. A total of 15 OSCA proteins, distributed on 10 chromosomes, were identified in the sunflower, and all of them were located in the endoplasmic reticulum. Using the phylogenetic tree, collinearity, gene structure, and motif analysis of the six Compositae species and six other plants, we found that the sunflower OSCA protein had only three subfamilies and lacked the Group 4 subfamily, which is conserved in the evolution of Compositae and subject to purification selection. The OSCA gene structure and motif analysis of the sunflower and six Compositae showed that there was a positive correlation between the number of motifs of most genes and the length of the gene, different subfamilies had different motifs, and the Group 4 subfamily had the smallest number of genes and the simplest gene structure. RNA-seq and qRT-PCR analysis showed that the expression levels of most OSCA genes in the sunflower changed to varying degrees under salt stress, and HaOSCA2.6 and HaOSCA3.1 were the most important in the sunflower's response to salt stress. The coexpression network of the sunflower genes under salt stress was constructed based on weighted gene co-expression network analysis (WGCNA). In conclusion, our findings suggest that the OSCA gene family is conserved during the sunflower's evolution and plays an important role in salt tolerance. These results will deepen our understanding of the evolutionary relationship of the sunflower OSCA gene family and provide a basis for their functional studies under salt stress.

Evaluating and Validating Sunflower Reference Genes for Q-PCR Studies Under High Temperature Condition.

Q-PCR is the method of choice for PCR- based transcriptomics and validating microarray-based and RNA-seq results. Proper application of this technology requires proper normalization to correct as much as possible errors propagating during RNA extraction and cDNA synthesis. The investigation was performed to find stable reference genes in sunflower under shifting in ambient temperature. Sequences of five well-known reference genes of Arabidopsis (Actin, Ubiquitin, Elongation factor-1, GAPDH, and SAND) and one well-known reference gene inhuman, Importin, were subjected to BLASTX against sunflower databases and the relevant genes were subjected to primer designing for q-PCR. Two sunflower inbred lines were cultivated at two dates so that anthesis occurred at nearly 30 °C and 40 °C (heat stress). The experiment was repeated for two years. Q-PCR was run on samples taken for two planting date separately at the beginning of anthesis for each genotype from leaf, taproots, receptacle base, immature and mature disc flowers and on pooled samples comprising of the tissues for each genotype, planting dates and also all tissues for both genotypes and both planting dates. Basic statistical properties of each candidate gene across all the samples were calculated. Furthermore, gene expression stability analysis was done for six candidate reference genes on Cq mean of two years using three independent algorithms, geNorm, Bestkeeper, and Refinder. Designed primers for Actin2, SAND, GAPDH, Ubiquitin, EF-1a, and Importin yielded a single peak in melting curve analysis indicating specificity of the PCR reaction. Basic statistical analysis showed that Actin2 and EF-1a had the highest and lowest expression levels across all the samples, respectively. Actin2 appeared to be the most stable reference gene across all the samples based on the three used algorithms. Pairwise variation analysis revealed that for samples taken under ambient temperature of 30 °C, Actin2, EF-1a, SAND and for those taken under ambient temperature of 40 °C, Actin2, EF-1a, Importin and SAND have to be used for normalization in q-PCR studies. Moreover, it is suggested that normalization to be based on Actin2, SAND and EF-1a for vegetative tissues and Actin2, EF-1a, SAND and Importin for reproductive tissues. In the present research, proper reference genes for normalization of gene expression studies under heat stress conditions were introduced. Moreover, the presence of genotype-by- planting date interaction effects and tissue specific gene expression pattern on the behavior of the most three stable reference genes was indicated.

The genomics of linkage drag in inbred lines of sunflower

Crop wild relatives represent valuable sources of alleles for crop improvement, including adaptation to climate change and emerging diseases. However, introgressions from wild relatives might have deleterious effects on desirable traits, including yield, due to linkage drag. Here, we analyzed the genomic and phenotypic impacts of wild introgressions in inbred lines of cultivated sunflower to estimate the impacts of linkage drag. First, we generated reference sequences for seven cultivated and one wild sunflower genotype, as well as improved assemblies for two additional cultivars. Next, relying on previously generated sequences from wild donor species, we identified introgressions in the cultivated reference sequences, as well as the sequence and structural variants they contain. We then used a ridge-regression best linear unbiased prediction (BLUP) model to test the effects of the introgressions on phenotypic traits in the cultivated sunflower association mapping population. We found that introgression has introduced substantial sequence and structural variation into the cultivated sunflower gene pool, including >3,000 new genes. While introgressions reduced genetic load at protein-coding sequences, they mostly had negative impacts on yield and quality traits. Introgressions found at high frequency in the cultivated gene pool had larger effects than low-frequency introgressions, suggesting that the former likely were targeted by artificial selection. Also, introgressions from more distantly related species were more likely to be maladaptive than those from the wild progenitor of cultivated sunflower. Thus, breeding efforts should focus, as far as possible, on closely related and fully compatible wild relatives.

Genome-wide identification and characterization of exapted transposable elements in the large genome of sunflower (Helianthus annuus L.).

Transposable elements (TEs) are an important source of genome variability, playing many roles in the evolution of eukaryotic species. Besides well-known phenomena, TEs may undergo the exaptation process and generate the so-called exapted transposable element genes (ETEs). Here we present a genome-wide survey of ETEs in the large genome of sunflower (Helianthus annuus L.), in which the massive amount of TEs, provides a significant source for exaptation. A library of sunflower TEs was used to build TE-specific Hidden Markov Model profiles, to search for all available sunflower gene products. In doing so, 20 016 putative ETEs were identified and further investigated for the characteristics that distinguish TEs from genes, leading to the validation of 3530 ETEs. The analysis of ETEs transcription patterns under different stress conditions showed a differential regulation triggered by treatments mimicking biotic and abiotic stress; furthermore, the distribution of functional domains of differentially regulated ETEs revealed a relevant presence of domains involved in many aspects of cellular functions. A comparative genomic investigation was performed including species representative of Asterids and appropriate outgroups: the bulk of ETEs that resulted were specific to the sunflower, while few ETEs presented orthologues in the genome of all analyzed species, making the hypothesis of a conserved function. This study highlights the crucial role played by exaptation, actively contributing to species evolution.

Citric acid assisted phytoextraction of nickle from soil helps to tolerate oxidative stress and expression profile of NRAMP genes in sunflower at different growth stages.

Soil polluted with Nickel (Ni) adversely affects sunflower growth resulting in reduced yield. Counterbalancing Ni toxicity requires complex molecular, biochemical, and physiological mechanisms at the cellular, tissue, and whole plant levels, which might improve crop productivity. One of the primary adaptations to tolerate Ni toxicity is the enhanced production of antioxidant enzymes and the elevated expression of Ni responsive genes. In this study, biochemical parameters, production of ROS, antioxidants regulation, and expression of NRAMP metal transporter genes were studied under Ni stress in sunflower. There were four soil Ni treatments (0, 50, 100, and 200 mg kg-1 soil), while citric acid (CA, 5 mM kg-1 soil) was applied on the 28th and 58th days of plant growth. The samples for all analyses were obtained on the 30th and 60th day of plant growth, respectively. The results indicated that the concentrations of Ni in roots and shoots were increased with increasing concentrations of Ni at both time intervals. Proline contents, ascorbic acid, protein, and total phenolics were reduced under Ni-stress, but with the application of CA, improvement was witnessed in their contents. The levels of malondialdehyde and hydrogen peroxide were enhanced with the increasing concentration of Ni, and after applying CA, they were reduced. The contents of antioxidants, i.e., catalase, peroxidase, superoxide dismutase, ascorbate peroxidase, dehydroascorbate reductase, and glutathione reductase, were increased at 50 ppm Ni concentration and decreased at higher concentrations of Ni. The application of CA significantly improved antioxidants at all concentrations of Ni. The enhanced expression of NRAMP1 (4, 51 and 81 folds) and NRAMP3 (1.05, 4 and 6 folds) was found at 50, 100 and 200ppm Ni-stress, respectively in 30 days old plants and the same pattern of expression was recorded in 60 days old plants. CA further enhanced the expression at both developmental stages. In conclusion, CA enhances Ni phytoextraction efficiency as well as protect plant against oxidative stress caused by Ni in sunflower.

Phylogenetic analysis and expression profiles of jasmonate ZIM-domain gene family provide insight into abiotic stress resistance in sunflower.

Jasmonate ZIM-domain (JAZ) proteins act as inhibitory factors of the jasmonic acid (JA) pathway, which is involved in regulating plant development and defense responses. However, there are no extensive studies available on JAZ genes in sunflower (Helianthus annuus L.). In this study, the phylogenetic analysis of 139 putative JAZ genes from eight plants demonstrated that these JAZs could be divided into five groups (Groups I–V), and the 27 sunflower JAZs (HaJAZs) were classified into these five groups. All groups contained genes from both monocotyledons and dicotyledons, indicating that the emergence of JAZ genes predates the differentiation of monocotyledons and dicotyledons. Both segmental and tandem duplications contributed greatly to this gene family’s expansion in sunflower, especially in Group II. Moreover, the expression profiles of HaJAZ genes under normal conditions, hormone treatments or abiotic stresses were analyzed based on RNA-seq data. HaJAZ2 may be undergoing pseudogenization as a nonfunctional gene because it was not expressed in any tissue. Many HaJAZ genes in roots upregulated their expression when involved in responding to exogenous hormones, especially methyl-jasmonate. The abiotic stress treatments of sunflower showed that HaJAZ5, HaJAZ15, HaJAZ17, HaJAZ20, and HaJAZ21 tend to be sensitive to certain abiotic stresses. HaJAZs from different groups may share similar functions but also exercise their unique functions when responding to abiotic stresses. We speculated that this gene family was conserved in sequence but varied in its expression among duplicated HaJAZ genes, which implies that they may confer neofunctionalization in the adaptation to abiotic stresses; this work provides insight into the resistance of sunflowers and their adaptation to diverse environmental conditions.

The Sunflower WRINKLED1 Transcription Factor Regulates Fatty Acid Biosynthesis Genes through an AW Box Binding Sequence with a Particular Base Bias.

Sunflower is an important oilseed crop in which the biochemical pathways leading to seed oil synthesis and accumulation have been widely studied. However, how these pathways are regulated is less well understood. The WRINKLED1 (WRI1) transcription factor is considered a key regulator in the control of triacylglycerol biosynthesis, acting through the AW box binding element (CNTNG(N)7CG). Here, we identified the sunflower WRI1 gene and characterized its activity in electrophoretic mobility shift assays. We studied its role as a co-regulator of sunflower genes involved in plastidial fatty acid synthesis. Sunflower WRI1-targets included genes encoding the pyruvate dehydrogenase complex, the α-CT and BCCP genes, genes encoding ACPs and the fatty acid synthase complex, together with the FATA1 gene. As such, sunflower WRI1 regulates genes involved in seed plastidial fatty acid biosynthesis in a coordinated manner, establishing a WRI1 push and pull strategy that drives oleic acid synthesis for its export into the cytosol. We also determined the base bias at the N positions in the active sunflower AW box motif. The sunflower AW box is sequence-sensitive at the non-conserved positions, enabling WRI1-binding. Moreover, sunflower WRI1 could bind to a non-canonical AW-box motif, opening the possibility of searching for new target genes.

Expressing the sunflower transcription factor HaHB11 in maize improves waterlogging and defoliation tolerance.

The sunflower (Helianthus annuus) transcription factor HaHB11 (H. annuus Homeobox 11) belongs to the homeodomain-leucine zipper family and confers improved yield to maize (Zea mays) hybrids (HiII × B73) and lines. Here we report that transgenic maize lines expressing HaHB11 exhibited better performance under waterlogging, both in greenhouse and field trials carried out during three growth cycles. Transgenic plants had increased chlorophyll content, wider stems, more nodal roots, greater total aerial biomass, a higher harvest index, and increased plant grain yield. Under severe defoliation caused by a windstorm during flowering, transgenic genotypes were able to set more grains than controls. This response was confirmed in controlled defoliation assays. Hybrids generated by crossing B73 HaHB11 lines with the contrasting Mo17 lines were also tested in the field and exhibited the same beneficial traits as the parental lines, compared with their respective controls. Moreover, they were less penalized by stress than commercial hybrids. Waterlogging tolerance increased via improvement of the root system, including more xylem vessels, reduced tissue damage, less superoxide accumulation, and altered carbohydrate metabolism. Multivariate analyses corroborated the robustness of the differential traits observed. Furthermore, canopy spectral reflectance data, computing 29 vegetation indices associated with biomass, chlorophyll, and abiotic stress, helped to distinguish genotypes as well as their growing conditions. Altogether the results reported here indicate that this sunflower gene constitutes a suitable tool to improve maize plants for environments prone to waterlogging and/or wind defoliation.

Expansion of CONSTANS-like genes in sunflower confers putative neofunctionalization in the adaptation to abiotic stresses

CONSTANS-like (COL) genes play crucial roles in the regulation of photoperiodic flowering and responses to biotic and abiotic stresses; however, COL genes in sunflower (HaCOL) have not been extensively studied. In the present study, we identified 22 putative HaCOL genes in the whole genome sequence of sunflower, which were unevenly distributed on 10 chromosomes. The phylogenetic analysis showed that the HaCOLs could be divided into three well-defined groups (groups I, II and III). Group III had the highest number of COL genes among the three tested monocots, while the highest number of COL genes were observed in group I among the five tested dicots. Among all eight species, group II had the fewest COL family members. Segmental duplications contributed greatly to the expansion of this gene family. Furthermore, 11 tissue expression profiles of 22 HaCOL genes were analyzed through RNA-seq, which displayed their tissue-specific expression profiles. In addition, the expression levels of these HaCOL genes were analyzed under hormone, cadmium (Cd), heat, and drought stresses, and the results showed that HaCOL3, HaCOL6, and HaCOL19 were more sensitive than other HaCOLs to certain abiotic stresses. Moreover, the duplicated genes conferred important neofunctionalization in response to abiotic stresses. On the basis of our findings, we speculate that this conserved, duplicated and neofunctionalized COL gene family may play pivotal roles in the adaptation of sunflower to adverse environments.

Comparative genomic analysis of MYB transcription factors for cuticular wax biosynthesis and drought stress tolerance in Helianthus annuus L.

Sunflower is an important oil-seed crop in Pakistan, it is mainly cultivated in the spring season. It is severely affected by drought stress resulting in lower yield. Cuticular wax acts as the first defense line to protect plants from drought stress condition. It seals the aerial parts of plants and reduce the water loss from leaf surfaces. Various myeloblastosis (MYB) transcription factors (TFs) are involved in biosynthesis of epicuticular waxes under drought-stress. However, less information is available for MYB, TFs in drought stress and wax biosynthesis in sunflower. We used different computational tools to compare the Arabidopsis MYB, TFs involved in cuticular wax biosynthesis and drought stress tolerance with sunflower genome. We identified three putative MYB genes (MYB16, MYB94 and MYB96) in sunflower along with their seven homologs in Arabidopsis. Phylogenetic association of MYB TFs in Arabidopsis and sunflower indicated strong conservation of TFs in plant species. From gene structure analysis, it was observed that intron and exon organization was family-specific. MYB TFs were unevenly distributed on sunflower chromosomes. Evolutionary analysis indicated the segmental duplication of the MYB gene family in sunflower. Quantitative Real-Time PCR revealed the up-regulation of three MYB genes under drought stress. The gene expression of MYB16, MYB94 and MYB96 were found many folds higher in experimental plants than control. The present study provided the first insight into MYB TFs family's characterization in sunflower under drought stress conditions and wax biosynthesis TFs.

A TILLING by sequencing approach to identify induced mutations in sunflower genes

The Targeting Induced Local Lesions in Genomes (TILLING) technology is a reverse genetic strategy broadly applicable to every kind of genome and represents an attractive tool for functional genomic and agronomic applications. It consists of chemical random mutagenesis followed by high-throughput screening of point mutations in targeted genomic regions. Although multiple methods for mutation discovery in amplicons have been described, next-generation sequencing (NGS) is the tool of choice for mutation detection because it quickly allows for the analysis of a large number of amplicons. The aim of the present work was to screen a previously generated sunflower TILLING population and identify alterations in genes involved in several important and complex physiological processes. Twenty-one candidate sunflower genes were chosen as targets for the screening. The TILLING by sequencing strategy allowed us to identify multiple mutations in selected genes and we subsequently validated 16 mutations in 11 different genes through Sanger sequencing. In addition to addressing challenges posed by outcrossing, our detection and validation of mutations in multiple regulatory loci highlights the importance of this sunflower population as a genetic resource.

Integration of early disease-resistance phenotyping, histological characterization, and transcriptome sequencing reveals insights into downy mildew resistance in impatiens

Downy mildew (DM), caused by obligate parasitic oomycetes, is a destructive disease for a wide range of crops worldwide. Recent outbreaks of impatiens downy mildew (IDM) in many countries have caused huge economic losses. A system to reveal plant–pathogen interactions in the early stage of infection and quickly assess resistance/susceptibility of plants to DM is desired. In this study, we established an early and rapid system to achieve these goals using impatiens as a model. Thirty-two cultivars of Impatiens walleriana and I. hawkeri were evaluated for their responses to IDM at cotyledon, first/second pair of true leaf, and mature plant stages. All I. walleriana cultivars were highly susceptible to IDM. While all I. hawkeri cultivars were resistant to IDM starting at the first true leaf stage, many (14/16) were susceptible to IDM at the cotyledon stage. Two cultivars showed resistance even at the cotyledon stage. Histological characterization showed that the resistance mechanism of the I. hawkeri cultivars resembles that in grapevine and type II resistance in sunflower. By integrating full-length transcriptome sequencing (Iso-Seq) and RNA-Seq, we constructed the first reference transcriptome for Impatiens comprised of 48,758 sequences with an N50 length of 2060 bp. Comparative transcriptome and qRT-PCR analyses revealed strong candidate genes for IDM resistance, including three resistance genes orthologous to the sunflower gene RGC203, a potential candidate associated with DM resistance. Our approach of integrating early disease-resistance phenotyping, histological characterization, and transcriptome analysis lay a solid foundation to improve DM resistance in impatiens and may provide a model for other crops.

Genome‑wide identification and analysis of the trihelix transcription factors in sunflower

The trihelix genes encode plant-specific transcription factors, which play a vital role in plant morphological and developmental processes. However, information about the presence of trihelix genes in sunflower (Helianthus annuus L.) is scarce. Sunflower belongs to composite family and possesses strong drought and salt-alkali tolerance. In this study based on H. annuus genome data, we have identified and analyzed the trihelix genes with a complete description of their physical and chemical properties, phylogenetic relationships, motif composition, chromosome distribution, exon-intron structure, cis-acting elements, and chromosome collinearity. In H. annuus, 31 full-length trihelix genes were identified and categorized into six subgroups (SIP, GT1, SH4, Gδ, GT-γ, and GT2). Multiple Em for motif elicitation (MEME), used for conservative motif analysis, identified 10 distinct motifs unevenly distributed on 31 trihelix genes. In addition to that, chromosome localization analysis showed the number and distribution of these trihelix genes on 17 chromosomes of H. annuus. Transcriptional structure analysis revealed the structure of introns and exons of different gene members. Furthermore, cis-element analysis identified 19 different types of cis-elements mainly related to abiotic stress, hormones, and growth and development of plant. Results of this study manifested novel insights into phylogenetic relationships and possible functions of H. annuus trihelix genes. Moreover, these findings can assist in future studies regarding specific physiological effects of H. annuus trihelix transcription factors.

Molecular characterization of Fe-acquisition genes causing decreased Fe uptake and photosynthetic inefficiency in Fe-deficient sunflower

Iron (Fe) deficiency in plants hinders growth and yield. Thus, this study aims to elucidate the responses and molecular characterization of genes in Fe-deficient sunflower. The study was conducted on 14 days-old sunflower plants cultivated in hydroponic culture under Fe-sufficient and Fe-deficient conditions. The Fe-starved sunflower showed substantial decrease in plant biomass, SPAD score, quantum yield efficiency of PSII (Fv/Fm), photosynthetic performance index (Pi_ABS). Further, Fe shortage reduced Fe and Zn concentrations in roots and shoots, accompanied by a marked decrease of HaNramp1 and HaZIP1 expression in roots, suggesting the association of Zn status contributing to photosynthetic inefficiency in sunflower. The ferric chelate reductase (FCR) activity, along with HaFRO2 and HaIRT1 transcripts, were constitutively expressed, suggesting that sunflower plants can regulate FCR activity, although the lack of bioavailable Fe in the rhizosphere strongly corresponds to the limited Fe uptake in sunflower. The substantial increase of proton extrusion in roots and the localization of Fe-related genes in the plasma membrane are also evident in sunflower as common responses to Fe-deficiency by this Strategy I plant species. Analysis showed that three motifs of Fe-related proteins were linked to the ZIP zinc transporter. The interactome map revealed the close partnership of these Fe-related genes in addition to FRU gene encoding putative transcription factor linked to Fe uptake response. The cis-regulatory analysis of promoter suggested the involvement of auxin, salicylic acid, and methyl jasmonate-responsive elements in the regulatory process in response to Fe deficiency. These findings may be beneficial to develop Fe-efficient sunflower plants through breeding or genome editing approaches.