Overexpression of an EIN3-binding F-box protein2-like gene caused elongated fruit shape and delayed fruit development and ripening in tomato

Integrative Analysis of Metabolome and Transcriptome of Carotenoid Biosynthesis Reveals the Mechanism of Fruit Color Change in Tomato (Solanum lycopersicum)

Tomato fruit ripening is accompanied by carotenoid accumulation and color changes. To elucidate the regulatory mechanisms underlying carotenoid synthesis during fruit ripening, a combined transcriptomic and metabolomic analysis was conducted on red-fruited tomato (WP190) and orange-fruited tomato (ZH108). A total of twenty-nine (29) different carotenoid compounds were identified in tomato fruits at six different stages. The abundance of the majority of the carotenoids was enhanced significantly with fruit ripening, with higher levels of lycopene; (E/Z)-lycopene; and α-, β- and γ-carotenoids detected in the fruits of WP190 at 50 and 60 days post anthesis (DPA). Transcriptome analysis revealed that the fruits of two varieties exhibited the highest number of differentially expressed genes (DEGs) at 50 DPA, and a module of co-expressed genes related to the fruit carotenoid content was established by WGCNA. qRT-PCR analysis validated the transcriptome result with a significantly elevated transcript level of lycopene biosynthesis genes (including SlPSY2, SlZCIS, SlPDS, SlZDS and SlCRTSO2) observed in WP190 at 50 DPA in comparison to ZH108. In addition, during the ripening process, the expression of ethylene biosynthesis (SlACSs and SlACOs) and signaling (SlEIN3 and SlERF1) genes was also increased, and these mechanisms may regulate carotenoid accumulation and fruit ripening in tomato. Differential expression of several key genes in the fruit of two tomato varieties at different stages regulates the accumulation of carotenoids and leads to differences in color between the two varieties of tomato. The results of this study provide a comprehensive understanding of carotenoid accumulation and ethylene biosynthesis and signal transduction pathway regulatory mechanisms during tomato fruit development.

Molecular Basis of Plant-Pathogen Interactions in the Agricultural Context

Biotic stressors pose significant threats to crop yield, jeopardizing food security and resulting in losses of over USD 220 billion per year by the agriculture industry. Plants activate innate defense mechanisms upon pathogen perception and invasion. The plant immune response comprises numerous concerted steps, including the recognition of invading pathogens, signal transduction, and activation of defensive pathways. However, pathogens have evolved various structures to evade plant immunity. Given these facts, genetic improvements to plants are required for sustainable disease management to ensure global food security. Advanced genetic technologies have offered new opportunities to revolutionize and boost plant disease resistance against devastating pathogens. Furthermore, targeting susceptibility (S) genes, such as OsERF922 and BnWRKY70, through CRISPR methodologies offers novel avenues for disrupting the molecular compatibility of pathogens and for introducing durable resistance against them in plants. Here, we provide a critical overview of advances in understanding disease resistance mechanisms. The review also critically examines management strategies under challenging environmental conditions and R-gene-based plant genome-engineering systems intending to enhance plant responses against emerging pathogens. This work underscores the transformative potential of modern genetic engineering practices in revolutionizing plant health and crop disease management while emphasizing the importance of responsible application to ensure sustainable and resilient agricultural systems.

Cytological, Phytohormone, and Transcriptome Analyses Provide Insights into Persimmon Fruit Shape Formation (Diospyros kaki Thunb.)

Fruit shape is an important external feature when consumers choose their preferred fruit varieties. Studying persimmon (Diospyros kaki Thunb.) fruit shape is beneficial to increasing its commodity value. However, research on persimmon fruit shape is still in the initial stage. In this study, the mechanism of fruit shape formation was studied by cytological observations, phytohormone assays, and transcriptome analysis using the long fruit and flat fruit produced by 'Yaoxianwuhua' hermaphroditic flowers. The results showed that stage 2-3 (June 11-June 25) was the critical period for persimmon fruit shape formation. Persimmon fruit shape is determined by cell number in the transverse direction and cell length in the longitudinal direction. High IAA, GA4, ZT, and BR levels may promote long fruit formation by promoting cell elongation in the longitudinal direction, and high GA3 and ABA levels may be more conducive to flat fruit formation by increasing the cell number in the transverse direction and inhibiting cell elongation in the longitudinal direction, respectively. Thirty-two DEGs related to phytohormone biosynthesis and signaling pathways and nine DEGs related to cell division and cell expansion may be involved in the persimmon fruit shape formation process. These results provide valuable information for regulatory mechanism research on persimmon fruit formation.

A cluster of putative resistance genes is associated with a dominant resistance to sunflower broomrape

KEY MESSAGE

The HaOr5 resistance gene is located in a large genomic insertion containing putative resistance genes and provides resistance to O. cumana, preventing successful connection to the sunflower root vascular system. Orobanche cumana (sunflower broomrape) is a parasitic plant that is part of the Orobanchaceae family and specifically infests sunflower crops. This weed is an obligate parasitic plant that does not carry out photosynthetic activity or develop roots and is fully dependent on its host for its development. It produces thousands of dust-like seeds per plant. It possesses a high spreading ability and has been shown to quickly overcome resistance genes successively introduced by selection in cultivated sunflower varieties. The first part of its life cycle occurs underground. The connection to the sunflower vascular system is essential for parasitic plant survival and development. The HaOr5 gene provides resistance to sunflower broomrape race E by preventing the connection of O. cumana to the root vascular system. We mapped a single position of the HaOr5 gene by quantitative trait locus mapping using two segregating populations. The same location of the HaOr5 gene was identified by genome-wide association. Using a large population of thousands of F2 plants, we restricted the location of the HaOr5 gene to a genomic region of 193 kb. By sequencing the whole genome of the resistant line harboring the major resistance gene HaOr5, we identified a large insertion of a complex genomic region containing a cluster of putative resistance genes.

The Zinc Finger Protein MaCCCH33-Like2 Positively Regulates Banana Fruit Ripening by Modulating Genes in Starch and Cell Wall Degradation

As zinc finger protein transcription factors (TFs), the molecular mechanism of Cys-Cys-Cys-His (CCCH) TFs in regulating plant development, growth and stress response has been well studied. However, the roles of CCCH TFs in fruit ripening are still obscure. Herein, we report that MaCCCH33-like2 TF and its associated proteins modulate the fruit softening of 'Fenjiao' bananas. MaCCCH33-like2 interacts directly with the promoters of three genes: isoamylase2 (MaISA2), sugar transporter14-like (MaSUR14-like) and β-d-xylosidase23 (MaXYL23), all of which are responsible for encoding proteins involved in the degradation of starch and cell wall components. Additionally, MaCCCH33-like2 forms interactions with abscisic acid-insensitive 5 (ABI5)-like and ethylene F-box protein 1 (MaEBF1), resulting in enhanced binding and activation of promoters of genes related to starch and cell wall degradation. When MaCCCH33-like2 is transiently and ectopically overexpressed in 'Fenjiao' banana and tomato fruit, it facilitates softening and ripening processes by promoting the degradation of cell wall components and starch and the production of ethylene. Conversely, the temporary silencing of MaCCCH33-like2 using virus-induced gene silencing (VIGS) inhibits softening and ripening in the 'Fenjiao' banana by suppressing ethylene synthesis, as well as starch and cell wall degradation. Furthermore, the promoter activity of MaCCCH33-like2 is regulated by MaABI5-like. Taken together, we have uncovered a novel MaCCCH33-like2/MaEBF1/MaABI5-like module that participates in fruit softening regulation in bananas.

Identification of Brassica rapa BrEBF1 homologs and their characterization in cold signaling

EIN3-binding F-box 1 (EBF1) is involved in cold tolerance in Arabidopsis; however, its exact roles in cold signaling in Brassica rapa remain uncertain. Herein, we demonstrated that EBF1 homologs are highly conserved in Brassica species, but their copy numbers are diverse, with some motifs being species specific. Cold treatment activated the expression of EBF1 homologs BrEBF1 and BrEBF2 in B. rapa; however, their expression schemas were diverse in different cold-resistant varieties of the plant. Subcellular localization analysis revealed that BrEBF1 is a nuclear-localized F-box protein, and cold treatment did not alter its localization but induced its degradation. BrEBF1 overexpression enhanced cold tolerance, reduced cold-induced ROS accumulation, and enhanced MPK3 and MPK6 kinase activity in Arabidopsis. Our study revealed that BrEBF1 positively regulates cold tolerance in B. rapa and that BrEBF1-regulated cold tolerance is associated with ROS scavenging and MPK3 and MPK6 kinase activity through the C-repeat binding factor pathway.

Molecular and genetic regulations of fleshy fruit shape and lessons from Arabidopsis and rice

Fleshy fruit shape is an important external quality trait influencing the usage of fruits and consumer preference. Thus, modification of fruit shape has become one of the major objectives for crop improvement. However, the underlying mechanisms of fruit shape regulation are poorly understood. In this review we summarize recent progress in the genetic basis of fleshy fruit shape regulation using tomato, cucumber, and peach as examples. Comparative analyses suggest that the OFP-TRM (OVATE Family Protein - TONNEAU1 Recruiting Motif) and IQD (IQ67 domain) pathways are probably conserved in regulating fruit shape by primarily modulating cell division patterns across fleshy fruit species. Interestingly, cucumber homologs of FRUITFULL (FUL1), CRABS CLAW (CRC) and 1-aminocyclopropane-1-carboxylate synthase 2 (ACS2) were found to regulate fruit elongation. We also outline the recent progress in fruit shape regulation mediated by OFP-TRM and IQD pathways in Arabidopsis and rice, and propose that the OFP-TRM pathway and IQD pathway coordinate regulate fruit shape through integration of phytohormones, including brassinosteroids, gibberellic acids, and auxin, and microtubule organization. In addition, functional redundancy and divergence of the members of each of the OFP, TRM, and IQD families are also shown. This review provides a general overview of current knowledge in fruit shape regulation and discusses the possible mechanisms that need to be addressed in future studies.

The involvement of Ein3-binding F-box protein PbrEBF3 in regulating ethylene signaling during Cuiguan pear fruit ripening

Ein3-binding F-box (EBF) proteins have been determined to modulate ethylene response processes by regulating EIN3/EIL protein degradation in Arabidopsis and tomato. However, the function of pear PbrEBFs in ethylene-dependent responses during fruit ripening remains unclear. In this study, PbrEBF1, PbrEBF2, and PbrEBF3 display contrasting expression patterns in response to ethylene and 1-MCP treatment. PbrEBF3 displayed potential fruit ripening-associated function in a transient expression experiment. Yeast two-hybrid (Y2H) and Firefly luciferase complementation imaging (LCI) assays indicated that PbrEBF3 interacts with PbrEIL1, PbrEIL2, and PbrEIL3 proteins. In turn, the transcription of PbrEBF3 is directly regulated by PbrEILs via a feedback loop. PbrEILs trigger a transcriptional cascade of PbrERF24 and finally affect ethylene synthesis. Overall, PbrEBF3 plays a central role in pear fruit ripening through mediation of the ethylene signaling pathway.

Identification of KFB Family in Moso Bamboo Reveals the Potential Function of PeKFB9 Involved in Stress Response and Lignin Polymerization

The Kelch repeat F-box (KFB) protein is an important E3 ubiquitin ligase that has been demonstrated to perform an important post-translational regulatory role in plants by mediating multiple biological processes. Despite their importance, KFBs have not yet been identified and characterized in bamboo. In this study, 19 PeKFBs were identified with F-box and Kelch domains; genes encoding these PeKFBs were unevenly distributed across 12 chromosomes of moso bamboo. Phylogenetic analysis indicated that the PeKFBs were divided into eight subclades based on similar gene structures and highly conserved motifs. A tissue-specific gene expression analysis showed that the PeKFBs were differentially expressed in various tissues of moso bamboo. All the promoters of the PeKFBs contained stress-related cis-elements, which was supported by the differentially expression of PeKFBs of moso bamboo under drought and cold stresses. Sixteen proteins were screened from the moso bamboo shoots' cDNA library using PeKFB9 as a bait through a yeast two-hybrid (Y2H) assay. Moreover, PeKFB9 physically interacted with PeSKP1-like-1 and PePRX72-1, which mediated the activity of peroxidase in proteolytic turnover. Taken together, these findings improved our understanding of PeKFBs, especially in response to stresses, and laid a foundation for revealing the molecular mechanism of PeKFB9 in regulating lignin polymerization by degrading peroxidase.

SlDREB3, a negative regulator of ABA responses, controls seed germination, fruit size and the onset of ripening in tomato

SlDREB3 was identified as a ripening up-regulated gene of the AP2/ERF-domain family of transcription factors. Its manipulation affects processes primarily governed by ABA. It negatively regulates ABA responses in tomato by altering ABA levels/signaling and is, in turn, negatively regulated by ABA. SlDREB3 over-expression lines show higher transcript levels of the ABA metabolism genes CYP707A3 and UGT75C1 and an 85% reduction in ABA levels leading to early seed germination. In contrast, suppression lines show decreased CYP707A3/UGT75C1 expression, 3-fold higher ABA levels and delayed germination. The expression of other ABA signaling and response genes is also affected. Suppression of SlDREB3 accelerates the onset of ripening by 4-5 days while its over-expression delays it and also reduces final fruit size. SlDREB3 manipulation effects large scale changes in the fruit transcriptome with suppression lines showing early increase in ABA levels and activation of most ripening pathway genes that govern ethylene, carotenoids and softening. Strikingly, key transcription factors like CNR, NOR, RIN, FUL1, governing ethylene-dependent and ethylene-independent aspects of ripening, are activated early upon SlDREB3 suppression suggesting their control by ABA. The studies identify SlDREB3 as a negative regulator of ABA responses across tissues and a key ripening regulator controlling ethylene-dependent and ethylene-independent aspects.

Genome-wide identification and characterization of F-box family proteins in sweet potato and its expression analysis under abiotic stress

In this study, genome-wide characterization of F-box proteins in sweet potato yielded 243 IbFBX genes, unevenly distributed on the 15 chromosomes of sweet potato. Gene duplication analysis suggested segmental duplication as the principal factor influencing the expansive evolution of IbFBX genes in sweet potato. Phylogenetic analysis clustered F-box proteins in sweet potato, Arabidopsis, and rice into six clades (I-VI). Gene structure analysis of the IbFBX genes revealed that most of the genes within the same clade were highly conserved. Expression profiles of IbFBX family genes in 9 different tissues and under stress conditions revealed that the IbFBXs were highly upregulated or downregulated in response to salt and drought stress, suggesting their significant roles in abiotic stress response and adaptation. Knowledge of the diverse functions and expression patterns of IbFBXs presents a solid theoretical basis for annotating the functions of IbFBXs and further facilitate the molecular breeding of sweet potato.

F-box protein EBF1 and transcription factor ABI5-like regulate banana fruit chilling-induced ripening disorder

Cold stress adversely affects plant production, both qualitatively and quantitatively. Banana (Musa acuminata) is sensitive to cold stress and suffers chilling injury (CI) when stored under 11°C, causing abnormal fruit softening. However, the mechanism underlying the abnormal fruit softening due to CI remains obscure. This study uncovered the coordinated transcriptional mechanism of ethylene F-box (EBF1) protein and abscisic acid-insensitive 5 (ABI5)-like protein in regulating chilling-induced softening disorders of Fenjiao banana. Cold stress severely inhibited the transcript and protein levels of EBF1, ABI5-like, and fruit softening-related genes. The ABI5-like protein bound to the promoters of key starch and cell wall degradation-related genes such as β-amylase 8 (BAM8), pectate lyase 8 (PL8), and β-D-xylosidase23-like (XYL23-like) and activated their activities. EBF1 physically interacted with ABI5-like and enhanced the transcriptional activity of the key starch and cell wall degradation-related genes but did not ubiquitinate or degrade ABI5-like protein. This promoted fruit ripening and ameliorated fruit CI in a manner similar to the effect of exogenous abscisic acid treatment. The ectopic and transient overexpression of EBF1 and ABI5-like genes in tomato (Solanum lycopersicum) and Fenjiao banana accelerated fruit ripening and softening by promoting ethylene production, starch and cell wall degradation, and decreasing fruit firmness. EBF1 interacted with EIL4 but did not ubiquitinate or degrade EIL4, which is inconsistent with the typical role of EBF1/2 in Arabidopsis (Arabidopsis thaliana). These results collectively highlight that the interaction of EBF1 and ABI5-like controls starch and cell wall metabolism in banana, which is strongly inhibited by chilling stress, leading to fruit softening and ripening disorder.

Genome and transcriptome-based characterization of high energy carbon-ion beam irradiation induced delayed flower senescence mutant in Lotus japonicus

BACKGROUND

Flower longevity is closely related to pollen dispersal and reproductive success in all plants, as well as the commercial value of ornamental plants. Mutants that display variation in flower longevity are useful tools for understanding the mechanisms underlying this trait. Heavy-ion beam irradiation has great potential to improve flower shapes and colors; however, few studies are available on the mutation of flower senescence in leguminous plants.

RESULTS

A mutant (C416) exhibiting blossom duration eight times longer than that of the wild type (WT) was isolated in Lotus japonicus derived from carbon ion beam irradiation. Genetic assays supported that the delayed flower senescence of C416 was a dominant trait controlled by a single gene, which was located between 4,616,611 Mb and 5,331,876 Mb on chromosome III. By using a sorting strategy of multi-sample parallel genome sequencing, candidate genes were narrowed to the gene CUFF.40834, which exhibited high identity to ethylene receptor 1 in other model plants. A physiological assay demonstrated that C416 was insensitive to ethylene precursor. Furthermore, the dynamic changes of phytohormone regulatory network in petals at different developmental stages was compared by using RNA-seq. In brief, the ethylene, jasmonic acid (JA), and salicylic acid (SA) signaling pathways were negatively regulated in C416, whereas the brassinosteroid (BR) and cytokinin signaling pathways were positively regulated, and auxin exhibited dual effects on flower senescence in Lotus japonicus. The abscisic acid (ABA) signaling pathway is positively regulated in C416.

CONCLUSION

So far, C416 might be the first reported mutant carrying a mutation in an endogenous ethylene-related gene in Lotus japonicus, rather than through the introduction of exogenous genes by transgenic techniques. A schematic of the flower senescence of Lotus japonicus from the perspective of the phytohormone regulatory network was provided based on transcriptome profiling of petals at different developmental stages. This study is informative for elucidating the molecular mechanism of delayed flower senescence in C416, and lays a foundation for candidate flower senescence gene identification in Lotus japonicus. It also provides another perspective for the improvement of flower longevity in legume plants by heavy-ion beam.

The interplay between ABA/ethylene and NAC TFs in tomato fruit ripening: a review

This review contains functional roles of NAC transcription factors in the transcriptional regulation of ripening in tomato fruit, describes the interplay between ABA/ethylene and NAC TFs in tomato fruit ripening. Fruit ripening is regulated by a complex network of transcription factors (TFs) and genetic regulators in response to endogenous hormones and external signals. Studying the regulation of fruit ripening has important significance for controlling fruit quality, enhancing nutritional value, improving storage conditions and extending shelf-life. Plant-specific NAC (named after no apical meristem (NAM), Arabidopsis transcription activator factor 1/2 (ATAF1/2) and Cup-shaped cotyledon (CUC2)) TFs play essential roles in plant development, ripening and stress responses. In this review, we summarize the recent progress on the regulation of NAC TFs in fruit ripening, discuss the interactions between NAC and other factors in controlling fruit development and ripening, and emphasize how NAC TFs are involved in tomato fruit ripening through the ethylene and abscisic acid (ABA) pathways. The signaling network regulating ripening is complex, and both hormones and individual TFs can affect the status or activity of other network participants, which can alter the overall ripening network regulation, including response signals and fruit ripening. Our review helps in the systematic understanding of the regulation of NAC TFs involved in fruit ripening and provides a basis for the development or establishment of complex ripening regulatory network models.

SlCAND1, encoding cullin-associated Nedd8-dissociated protein 1, regulates plant height, flowering time, seed germination, and root architecture in tomato

Silencing of SlCAND1 expression resulted in dwarfish, loss of apical dominance, early flowering, suppression of seed germination, and abnormal root architecture in tomato Cullin-RING E3 ligases (CRLs)-dependent ubiquitin proteasome system mediates degradation of numerous proteins that controls a wide range of developmental and physiological processes in eukaryotes. Cullin-associated Nedd8-dissociated protein 1 (CAND1) acts as an exchange factor allowing substrate recognition part exchange and plays a vital role in reactivating CRLs. The present study reports on the identification of SlCAND1, the only one CAND gene in tomato. SlCAND1 expression is ubiquitous and positively regulated by multiple plant hormones. Silencing of SlCAND1 expression using RNAi strategy resulted in a pleiotropic and gibberellin/auxin-associated phenotypes, including dwarf plant with reduced internode length, loss of apical dominance, early flowering, low seed germination percentage, delayed seed germination speed, short primary root, and increased lateral root proliferation and elongation. Moreover, application of exogenous GA₃ or IAA could partly rescue some SlCAND1-silenced phenotypes, and the expression levels of gibberellin/auxin-related genes were altered in SlCAND1-RNAi lines. These facts revealed that SlCAND1 is required for gibberellin/auxin-associated regulatory network in tomato. Although SlCAND1 is crucial for multiple developmental processes during vegetative growth stage, SlCAND1-RNAi lines didn't exhibit visible effect on fruit development and ripening. Meanwhile, we discussed that multiple physiological functions of SlCAND1 in tomato are different to previous report of its ortholog in Arabidopsis. Our study adds a new perspective on the functional roles of CAND1 in plants, and strongly supports the hypothesis that CAND1 and its regulated ubiquitin proteasome system are pivotal for plant vegetative growth but possibly have different roles in diverse plant species.

Investigation of the EIL/EIN3 Transcription Factor Gene Family Members and Their Expression Levels in the Early Stage of Cotton Fiber Development

The ethylene-insensitive3-like/ethylene-insensitive3 (EIL/EIN3) protein family can serve as a crucial factor for plant growth and development under diverse environmental conditions. EIL/EIN3 protein is a form of a localized nuclear protein with DNA-binding activity that potentially contributes to the intricate network of primary and secondary metabolic pathways of plants. In light of recent research advances, next-generation sequencing (NGS) and novel bioinformatics tools have provided significant breakthroughs in the study of the EIL/EIN3 protein family in cotton. In turn, this paved the way to identifying and characterizing the EIL/EIN3 protein family. Hence, the high-throughput, rapid, and cost-effective meta sequence analyses have led to a remarkable understanding of protein families in addition to the discovery of novel genes, enzymes, metabolites, and other biomolecules of the higher plants. Therefore, this work highlights the recent advance in the genomic-sequencing analysis of higher plants, which has provided a plethora of function profiles of the EIL/EIN3 protein family. The regulatory role and crosstalk of different metabolic pathways, which are apparently affected by these transcription factor proteins in one way or another, are also discussed. The ethylene hormone plays an important role in the regulation of reactive oxygen species in plants under various environmental stress circumstances. EIL/EIN3 proteins are the key ethylene-signaling regulators and play important roles in promoting cotton fiber developmental stages. However, the function of EIL/EIN3 during initiation and early elongation stages of cotton fiber development has not yet been fully understood. The results provided valuable information on cotton EIL/EIN3 proteins, as well as a new vision into the evolutionary relationships of this gene family in cotton species.

Genome-wide analysis and characterization of F-box gene family in Gossypium hirsutum L

Background

F-box proteins are substrate-recognition components of the Skp1-Rbx1-Cul1-F-box protein (SCF) ubiquitin ligases. By selectively targeting the key regulatory proteins or enzymes for ubiquitination and 26S proteasome mediated degradation, F-box proteins play diverse roles in plant growth/development and in the responses of plants to both environmental and endogenous signals. Studies of F-box proteins from the model plant Arabidopsis and from many additional plant species have demonstrated that they belong to a super gene family, and function across almost all aspects of the plant life cycle. However, systematic exploration of F-box family genes in the important fiber crop cotton (Gossypium hirsutum) has not been previously performed. The genome-wide analysis of the cotton F-box gene family is now possible thanks to the completion of several cotton genome sequencing projects.

Results

In current study, we first conducted a genome-wide investigation of cotton F-box family genes by reference to the published F-box protein sequences from other plant species. 592 F-box protein encoding genes were identified in the Gossypium hirsutume acc.TM-1 genome and, subsequently, we were able to present their gene structures, chromosomal locations, syntenic relationships with their parent species. In addition, duplication modes analysis showed that cotton F-box genes were distributed to 26 chromosomes, with the maximum number of genes being detected on chromosome 5. Although the WGD (whole-genome duplication) mode seems play a dominant role during cotton F-box gene expansion process, other duplication modes including TD (tandem duplication), PD (proximal duplication), and TRD (transposed duplication) also contribute significantly to the evolutionary expansion of cotton F-box genes. Collectively, these bioinformatic analysis suggest possible evolutionary forces underlying F-box gene diversification. Additionally, we also conducted analyses of gene ontology, and expression profiles in silico, allowing identification of F-box gene members potentially involved in hormone signal transduction.

Conclusion

The results of this study provide first insights into the Gossypium hirsutum F-box gene family, which lays the foundation for future studies of functionality, particularly those involving F-box protein family members that play a role in hormone signal transduction.

The Involvement of the Banana F-Box Protein MaEBF1 in Regulating Chilling-Inhibited Starch Degradation through Interaction with a MaNAC67-Like Protein

Low-temperature storage is a common strategy for preserving and transporting vegetables and fruits. However, many fruits are hypersensitive to chilling injury, including bananas. In the present study, storage conditions of 11 °C delayed the ripening of Fenjiao (Musa ABB Pisang Awak) banana, and the pulp could be softened after ethephon treatment. Storage conditions of 7 °C prevented fruit from fully softening, and fruit contained a significantly higher starch content and lower soluble sugar content. MaEBF1, a critical gene component in the ethylene signaling pathway, was repressed during ripening after fruit had been stored for 12 days at 7 °C. The expression of a series of starch degradation-related genes and a MaNAC67-like gene were also severely repressed. Both MaEBF1 and MaNAC67-like genes were ethylene-inducible and localized in the nucleus. MaNAC67-like protein was able to physically bind to the promoter of genes associated with starch degradation, including MaBAM6, MaSEX4, and MaMEX1. Yeast two-hybrid, GST-pull down, and BiFC assays showed that MaEBF1 interacted with the MaNAC67-like protein, and their interaction further activated the promoters of MaBAM6 and MaSEX4. The current study indicates that MaNAC67-like is a direct regulator of starch degradation and potential for involvement in regulating chilling-inhibited starch degradation by interacting with the ethylene signaling components in banana fruit. The present work paves the way for further functional analysis of MaEBF1 and MaNAC67-like in banana, which will be useful for understanding the regulation of banana starch metabolism and fruit ripening.