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Sex determination is a crucially important developmental event that is pervasive throughout nature and enhances the adaptation of species. Among plants, cucumber (Cucumis sativus L.) can generate both unisexual and bisexual flowers, and the sex type is mainly controlled by several 1-aminocyclopropane-1-carboxylic acid synthases (CsACSs). However, the regulatory mechanism of these synthases remains elusive. Here, we used gene expression analysis, protein–DNA interaction assays, and transgenic plants to study the function of a gynoecium-specific gene, ETHYLENE RESPONSE FACTOR31 (CsERF31), in female flower differentiation. We found that in a predetermined female flower, ethylene signaling activates CsERF31 by CsEIN3, and then CsERF31 stimulates CsACS2, which triggers a positive feedback loop to ensure female rather than bisexual flower development. A similar interplay is functionally conserved in melon (Cucumis melo L.). Knockdown of CsERF31 by RNAi causes defective bisexual flowers to replace female flowers. Ectopic expression of CsERF31 suppresses stamen development and promotes pistil development in male flowers, demonstrating that CsERF31 functions as a sex switch. Taken together, our data confirm that CsERF31 represents the molecular link between female–male determination and female–bisexual determination, and provide mechanistic insight into how ethylene promotes female flowers, rather than bisexual flowers, in cucumber sex determination.

Anthocyanin accumulation is transcriptionally regulated by the MYB–bHLH–WD40 complex. Light is indispensable for anthocyanin accumulation, and light-inducible MYB and HY5 were considered to promote anthocyanin accumulation in many fruits. Whether and how light-inducible bHLH transcription factor and HY5 regulate anthocyanin synthesis in strawberry is unknown. In this study, we identified a bHLH transcription factor, FvbHLH9, which was induced by light as well as FvHY5, and found that, similar to FvHY5, the transient overexpression and interference FvbHLH9 in strawberry fruits can promote and decrease anthocyanin accumulation, respectively, indicating FvbHLH9 functions as a positive regulator of anthocyanin biosynthesis. Furthermore, we confirmed that both FvHY5 and FvbHLH9 specifically bind to the promoter region of some key enzyme genes, including FvDFR, and the expression of FvDFR was activated through the heterodimer formation between FvHY5 and FvbHLH9. Finally, we confirmed that FvbHLH9-promoted anthocyanin accumulation is dependent on HY5–bHLH heterodimerisation in Arabidopsis. Our findings provide insights into a mechanism involving the synergistic regulation of light-dependent coloration and anthocyanin biosynthesis via a HY5–bHLH heterodimer formed by the interaction of FvHY5 and FvbHLH9 in strawberry fruits.

Flavonoids belong to the family of polyphenolic secondary metabolites and contribute to fruit quality traits. It has been shown that MBW complexes (MYB-bHLH-WD40) regulate the flavonoids biosynthesis in different plants, but only a limited number of MBW complexes have been identified in strawberry species in general. In this study, we identified 112 R2R3-MYB proteins in woodland strawberry; 12 of them were found to have potential functions in regulating flavonoids biosynthesis by phylogenetic analysis. qRT-PCR assays showed that FvMYB3, FvMYB9, FvMYB11, FvMYB22, FvMYB64, and FvMYB105 mostly expressed at green stage of fruit development, aligned with proanthocyanidins accumulation; FvMYB10 and FvMYB41 showed higher expression levels at turning and ripe stages, aligned with anthocyanins accumulation. These results suggest that different MYBs might be involved in flavonoids biosynthesis at specific stages. Furthermore, FvMYB proteins were demonstrated to interact with FvbHLH proteins and induce expression from the promoters of CHS2 and DFR2 genes, which encode key enzymes in flavonoids biosynthesis. The co-expression of FvMYB and FvbHLH proteins in strawberry fruits also promoted the accumulation of proanthocyanidins. These findings confirmed and provided insights into the biofunction of MBW components in the regulation of flavonoid biosynthesis in woodland strawberry.

Soil enzymes and microorganisms are both important to maintaining good soil quality and are also sensitive to changes in agricultural management. The individual effects of tillage, straw incorporation and nitrogen (N) fertilization on soil enzymes and microflora have been widely acknowledged, but their interactive effect remains largely unknown. In a 5–year in–situ field study, effects of rotary (RTS) and plow tillage (PTS) practices with straw incorporation combined with three N fertilization levels (0 kg N ha–1, CK; 187 kg N ha–1, MN; 337 kg N ha–1, HN) on soil enzyme activities and microbial communities were assessed. Our results showed that the activities of β–glucosidase (βG), N–acetylglucosaminidase (NAG) and acid phosphatase (APH) were improved in RTS+MN. The bacterial and fungal abundances in RTS+MN and RTS+HN were 1.27–27.51 times higher than those in other treatment groups. However, the bacterial and fungal alpha diversities were enhanced in PTS+MN and PTS+CK compared with other treatments, respectively. Proteobacteria and Basidiomycota were the predominant phylum for the respective bacterial and fungal communities. Moreover, significant interactive effects were found in the fungal community composition, but only minor impacts were observed on the bacterial community composition. Soil water content and penetration resistance contributed more to the soil enzyme activity and microbial community than other soil properties investigated, whereas there was a significant positive correlation between βG and APH activities and microbial abundance. These findings can provide new insights into tillage with straw incorporation and N fertilization on maize cultivation in northeast China.

Trichomes that cover the epidermis of aerial plant organs play multiple roles in plant protection. Compared with a unicellular trichome in model plants, the development mechanism of the multicellular trichome is largely unclear. Notably, variations in trichome development are often accompanied by defects in the biosynthesis of cuticle and secondary metabolites; however, major questions about the interactions between developmental differences in trichomes and defects in metabolic pathways remain unanswered. Here, we characterized the glabrous mutantmict/csgl1/cstbhvia combined metabolomic and transcriptomic analyses to extend our limited knowledge regarding multicellular trichome development and metabolism in cucumber.Mictwas found to be explicitly expressed within trichome cells. Transcriptomic analysis indicated that genes involved in flavonoid and cuticle metabolism are significantly downregulated inmictmutants. Further metabolomic analysis confirmed that flavonoids, lipids, and cuticle compositions are dramatically altered inmictmutants. Additional studies revealed thatMictregulates flavonoid, lipid, and cuticle biosynthesis by likely directly binding to downstream functional genes, such asCsTT4,CsFLS1,CsCER26, andCsMYB36. These findings suggest that specific metabolic pathways (e.g., flavonoids and cuticle components) are co-regulated byMictand provide insights into transcriptional regulation mechanisms of multicellular trichome development and its specific metabolism in cucumber.

Light is a key environmental cue that fundamentally regulates plant growth and development, which is mediated by the multiple photoreceptors including the blue light (BL) photoreceptor cryptochrome 1 (CRY1). The signaling mechanism of Arabidopsis thaliana CRY1 involves direct interactions with CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1)/SUPPRESSOR OF PHYA-105 1 and stabilization of COP1 substrate ELONGATED HYPOCOTYL 5 (HY5). H2A.Z is an evolutionarily conserved histone variant, which plays a critical role in transcriptional regulation through its deposition in chromatin catalyzed by SWR1 complex. Here we show that CRY1 physically interacts with SWC6 and ARP6, the SWR1 complex core subunits that are essential for mediating H2A.Z deposition, in a BL-dependent manner, and that BL-activated CRY1 enhances the interaction of SWC6 with ARP6. Moreover, HY5 physically interacts with SWC6 and ARP6 to direct the recruitment of SWR1 complex to HY5 target loci. Based on previous studies and our findings, we propose that CRY1 promotes H2A.Z deposition to regulate HY5 target gene expression and photomorphogenesis in BL through the enhancement of both SWR1 complex activity and HY5 recruitment of SWR1 complex to HY5 target loci, which is likely mediated by interactions of CRY1 with SWC6 and ARP6, and CRY1 stabilization of HY5, respectively.

The characterization of soil physicochemical properties and the resulting soil enzyme activity changes are crucial for understanding the effects of various tillage and straw management techniques on crop grain yield. In 2018&ndash, 2019, we conducted a field micro&ndash, plot experiment to determine the effects of tillage depth and straw management on the soil physicochemical properties, enzyme activity, and maize grain yield. Six treatments were employed, including straw removal (CK), straw mixed with (SM), and straw buried (SB) into the soil under tillage depths of 10 (D10) and 30 cm (D30). The results demonstrated that SM and SB significantly increased the soil nitrate (NO3&ndash, &ndash, N) content and decreased the ammonium (NH4+&ndash, N) content in the 0&ndash, 20 cm soil layer in 2018 relative to CK. SM had greater soil urease (URE) and acid phosphatase (APH) activities in the 0&ndash, 20 cm soil layer, and SB improved the soil APH activity at the 30&ndash, 40 cm depth in both seasons. D30 obtained a lower penetration resistance in the 10&ndash, 40 cm soil profile and higher soil organic carbon (SOC) and soil total nitrogen (STN) contents at the 30&ndash, 40 cm soil depth relative to D10. The soil enzyme activity was positively related to the soil nutrient content and negatively related to the soil penetration resistance in the 0&ndash, 20 cm soil layer, particularly in D30. Compared with CK, the grain yield was higher by 2.48&ndash, 17.51% for SM and 7.48&ndash, 24.46% for SB in 2018 and 2019, respectively. The structural equation model analysis suggested that the tillage depth mainly affected the soil penetration resistance (PR) and pH, however, straw management dominantly influenced the soil mineral N levels, leading to other soil property changes and crop production results. In conclusion, straw incorporation with deeper plow tillage might be an optimal straw return approach for soil quality improvement and sustainable maize production in northeast China.

Phytochrome B (phyB), the primary red light photoreceptor, promotes photomorphogenesis in Arabidopsis by interacting with the basic helix-loop-helix transcriptional factor PIF3 and inducing its phosphorylation and degradation. Heterotrimeric G proteins are known to regulate various developmental processes in plants and animals. In Arabidopsis, the G-protein β subunit AGB1 is known to repress photomorphogenesis. However, whether and how phyB and AGB1 coordinately regulate photomorphogenesis are largely unknown. Here we show that phyB physically interacts with AGB1 in a red light-dependent manner and that AGB1 interacts directly with PIF3. Moreover, we demonstrate that the AGB1-PIF3 interaction inhibits the association of PIF3 with phyB, leading to reduced phosphorylation and degradation of PIF3, whereas the phyB-AGB1 interaction represses the association of PIF3 with AGB1, resulting in enhanced phosphorylation and degradation of PIF3. Our results suggest that phyB and AGB1 antagonistically regulate PIF3 stability by dynamically interacting with each other and PIF3. This dynamic mechanism may allow plants to balance phyB and G-protein signaling to optimize photomorphogenesis.

Cryptochromes (CRYs) are blue light photoreceptors that mediate a variety of light responses in plants and animals, including photomorphogenesis, flowering, and circadian rhythms. The signaling mechanism by which Arabidopsis thaliana cryptochromes CRY1 and CRY2 promote photomorphogenesis involves direct interactions with COP1, a RING motif-containing E3 ubiquitin ligase, and its enhancer SPA1. Brassinosteroid (BR) is a key phytohormone involved in the repression of photomorphogenesis, and here, we show that the signaling mechanism of Arabidopsis CRY1 involves the inhibition of BR signaling. CRY1 and CRY2 physically interact with BES1-INTERACTING MYC-LIKE1 (BIM1), a basic helix-loop-helix protein. BIM1, in turn, interacts with and enhances the activity of BRI1-EMS SUPPRESSOR1 (BES1), a master transcription factor in the BR signaling pathway. In addition, CRY1 and CRY2 interact specifically with dephosphorylated BES1, the physiologically active form of BES1 that is activated by BR in a blue light-dependent manner. The CRY1-BES1 interaction leads to both the inhibition of BES1 DNA binding activity and the repression of its target gene expression. Our study suggests that the blue light-dependent, BR-induced interaction of CRY1 with BES1 is a tightly regulated mechanism by which plants optimize photomorphogenesis according to the availability of external light and internal BR signals.

The woodland strawberry, Fragaria vesca, is a model plant for the diverse Rosaceae family, which contains many valuable fruit and ornamental crops. Light is an important external environment factor which influences all aspects of plant growth and development, including fruit ripening. Transcription regulation of light will provide insights into effect of light for fruit ripening. We treat strawberry fruit with dark or light, and by the RNA-Seq method, compare transcriptional level between dark-treated and light-treated strawberry fruits. Additionally, we detect anthocyanin and sugar accumulation in two-treated conditions of fruits. Moreover, we detect the protein change of FvMYB10, a key regulator of anthocyanin biosynthesis, under dark and light. Light can promote anthocyanin and soluble sugar accumulation in mature fruit, and also increases the expression of aroma-related genes and stabilizes FvMYB10 protein. Our findings reveal that light is essential for anthocyanin and sugar accumulation and regulates FvMYB10 at transcriptional level and post-translation level.

CRY1 interacts with HBI1 in a blue light-dependent manner. CRY1 and HBI1 antagonistically regulate expression of genes promoting cell elongation and CRY1 represses HBI1’s transcriptional activity by inhibiting its DNA binding ability., Cryptochromes (CRYs) are blue light photoreceptors that mediate various light responses in plants and animals. In Arabidopsis, there are two homologous CRYs, CRY1 and CRY2, which mediate blue light inhibition of hypocotyl elongation. It is known that CRY2 interacts with CIB1, a basic helix–loop–helix (bHLH) transcriptional factor, to regulate transcription and floral induction. In this study, we performed yeast two-hybrid screening and identified CIB1 as a CRY1-interacting protein. Moreover, we demonstrated that CRY1 physically interacted with the close homolog of CIB1, HBI1, which is known to act downstream of brassinosteroid (BR) and gibberellin acid (GA) signaling pathways to promote hypocotyl elongation, in a blue light-dependent manner. Transgenic and genetic interaction studies showed that overexpression of HBI1 resulted in enhanced hypocotyl elongation under blue light and that HBI1 acted downstream of CRYs to promote hypocotyl elongation. Genome-wide gene expression analysis indicated that CRYs and HBI1 antagonistically regulated the expression of genes involved in regulating cell elongation. Moreover, we demonstrated that CRY1–HBI1 interaction led to inhibition of HBI1’s DNA binding activity and its target gene expression. Together, our results suggest that HBI1 acts as a new CRY1-interacting protein and that the signaling mechanism of CRY1 involves repression of HBI1 transcriptional activity by direct CRY1–HBI1 interaction.

Using map-based cloning of ts gene, we identified a new sort of gene involved in the initiation of multicellular tender spine in cucumber. The cucumber (Cucumis sativus L.) fruit contains spines on the surface, which is an extremely valuable quality trait affecting the selection of customers. In this study, we elaborated cucumber line NC072 with wild type (WT) hard fruit spines and its spontaneous mutant NC073, possessing tender and soft spines on fruits. The mutant trait was named as tender spines (ts), which is controlled by a single recessive nuclear gene. We identified the gene ts by map-based cloning with an F2 segregating population of 721 individuals generated from NC073 and WT line SA419-2. It was located between two markers Indel6239679 and Indel6349344, 109.7 kb physical distance on chromosome 1 containing fifteen putative genes. With sequencing and quantitative reverse transcription-polymerase chain reaction analysis, the Csa1G056960 gene was considered as the most possible candidate gene of ts. In the mutant, Csa1G056960 has a nucleotide change in the 5′ splicing site of the second intron, which causes different splicing to delete the second exon, resulting in a N-terminal deletion in the predicted amino acid sequence. The gene encodes a C-type lectin receptor-like tyrosine-protein kinase which would play an important role in the formation of cucumber fruit. This is firstly reported of a receptor kinase gene regulating the development of multicellular spines/trichomes in plants. The ts allele could accelerate the molecular breeding of cucumber soft spines.

FvMYB10 protein has been proved to be a transcriptional switch for anthocyanin biosynthesis in strawberry. A single nucleotide mutation in R2 domain of FvMYB10, named as FvmMYB10, is found to be responsible for the white color in strawberry variety 'Yellow Wonder'. However, the mechanism of FvmMYB10 suppresses anthocyanin biosynthesis in strawberry is largely unknown. Here, we show that the transcriptional level of FvMYB10 and key enzyme genes involved in anthocyanin biosynthesis in 'Yellow Wonder' were lower than that in red color variety 'Ruegen', especially at turning to ripening stage. The low expression level of FvmMYB10 may due to his inability to bind to its promoter region and activate its own expression. We found FvMYB10-overexpressing, but not FvmMYB10-overexpressing, promote anthocyanin accumulation in Arabidopsis and strawberry fruit despite of their similar expression levels. In addition, subcellular localization assay indicated that FvMYB10-YFP, but not FvmMYB10-YFP, localized to sub-nucleus foci (speckles) in the nucleus, implying the mutation of FvMYB10 might inhibit its transcription factor activity and eventually interfere with its function. Subsequently, we confirmed that FvMYB10 bind to the promoter region of some specific key enzyme genes, including FvCHS2 and FvDFR1 and activated their expression. While FvmMYB10 failed to binding and transcriptional activating these genes. Our findings provide insights into molecular mechanism of anthocyanin biosynthesis regulated by MYB10 in strawberry fruits.

Arabidopsis CRY1 and phyB are the primary blue and red light photoreceptors mediating blue and red light inhibition of hypocotyl elongation, respectively. Auxin is a pivotal phytohormone involved in promoting hypocotyl elongation. CRY1 and phyB interact with and stabilize auxin/indole acetic acid proteins (Aux/IAAs) to inhibit auxin signaling. The present study investigated whether photoreceptors might interact directly with Auxin Response Factors (ARFs) to regulate auxin signaling. Protein-protein interaction studies demonstrated that CRY1 and phyB interact physically with ARF6 and ARF8 through their N-terminal domains in a blue and red light-dependent manner, respectively. Moreover, the N-terminal DNA-binding domain of ARF6 and ARF8 is involved in mediating their interactions with CRY1. Genetic studies showed that ARF6 and ARF8 act partially downstream from CRY1 and PHYB to regulate hypocotyl elongation under blue and red light, respectively. Chromatin immunoprecipitation-PCR assays demonstrated that CRY1 and phyB mediate blue and red light repression of the DNA-binding activity of ARF6 and ARF6-target gene expression, respectively. Altogether, the results herein suggest that the direct repression of auxin-responsive gene expression mediated by the interactions of CRY1 and phyB with ARFs constitutes a new layer of the regulatory mechanisms by which light inhibits auxin-induced hypocotyl elongation.

Eggplant is rich in anthocyanins, which are the major secondary metabolites and beneficial to human health. We discovered that the anthocyanin biosynthesis of eggplant cultivar 'Lanshan Hexian' was regulated by light. In this study, we isolated two blue light receptor genes, SmCRY1 and SmCRY2, and negative/positive anthocyanin regulatory factors SmCOP1 and SmHY5 from eggplant. In terms of transcript levels, SmCRY1, SmCRY2 and SmHY5 were up-regulated by light, while SmCOP1 was down-regulated. Subsequently, the four genes were functionally complemented in phenotype of corresponding mutants, indicating that they act as counterparts of Arabidopsis genes. Yeast two-hybrid and bimolecular fluorescence complementation assays showed that SmCRY1 and SmCRY2 interact with SmCOP1 in a blue-light-dependent manner. It also obtained the result that SmCOP1 interacts with SmHY5 and SmMYB1. Furthermore, using yeast one-hybrid assay, we found that SmHY5 and SmMYB1 both bind the promoters of anthocyanin biosynthesis structural genes (SmCHS and SmDFR). Taken together, blue-light-triggered CRY1/CRY2-COP1 interaction creates the condition that HY5 and MYB1 combine with the downstream anthocyanin synthesis genes (CHS and DFR) in eggplant. Our finding provides a new working model by which light controls anthocyanin accumulation in eggplant.

Figure S10. Alignment of promoter sequence of CsUP from WT and up. (PDF 108 kb)

Figure S8. Genomic DNA sequence alignment of Cs535790 from WT and up (PDF 67 kb)

Figure S5. Alignment of predicted protein sequences between WT and CGN19839. The amino acid highlighted in red is the acid alternation (Ile47 in WT to Val47 in CGN19839) caused by the SNP in the first exon of Csa1G535800. The amino acids highlighted in yellow are abnormal in CGN19839 and the amino acids highlighted in blue are missing in CGN19839. The DnaJ domain at the C-terminal is underlined (PDF 81 kb)

Figure S3. Pedicel orientation of B1 and CGN19839 indicating that both inbred lines have the upward-pedicel phenotype (PDF 271 kb)

Table S1. Primers used for mapping, cloning and qPCR. (PDF 186â kb) (PDF 185 kb)

Figure S7. Alignment of coding sequence of CsUP from WT and up with 19 other cucumber lines. The whole coding sequence length is 1404 bp. The 491–495 bp position of up and B1 is the 5-bp deletion highlighted in blue. The 139 bp position of CGN19839 that altered from A to G is highlighted in red, and the 1234–1237 bp position in CGN19839 is the 4-bp deletion in blue (PDF 451 kb)

Figure S2. Partial results of linkage analysis with indel-CsUp demonstrating that this marker is co-segregated with the upward-pedicel phenotype (PDF 91 kb)

Figure S4. Structure of Csa1G535800 and two mutation sites in CGN19839. a Structure of Csa1G535800. Boxes and lines indicate exons and introns, respectively. Two green boxes in Csa1G535800 indicate the 5′ UTR and the 3′ UTR. Sequencing results revealed that, compared to WT, CGN19839 has a SNP in the first exon and a 4-bp deletion in the sixth exon of Csa1G535800. The yellow box shows the deletion sequence in CGN19839. b The position of the SNP and the 4-bp deletion in the encoding sequence. Sequencing results revealed that there was a SNP (‘A’ in C-8-6 and ‘G’ in CGN19839) at 139 bp and a 4-bp deletion at 1234–1237 bp from the ATG start codon (PDF 188 kb)

Figure S6. Genomic DNA sequence alignment of CsUP from WT, up and CGN19839 (PDF 231 kb)

Background Pedicel orientation can affect the female flower orientation and seed yield in cucumber. A spontaneous mutant possessing upward growth of pedicels was identified in the wild type inbred strain 9930 and named upward-pedicel (up). The morphological and genetic analyses of up were performed in this study. In order to clone the up gene, 933 F2 individuals and 524 BC1 individuals derived from C-8-6 (WT) and up were used for map-based cloning. Results up was mapped to a 35.2 kb physical interval on chromosome 1, which contains three predicted genes. Sequencing analysis revealed that a 5-bp deletion was found in the second exon of Csa1G535800, and it led to a frameshift mutation resulting in a premature stop codon. The candidate gene of CsUp (Csa1G535800) was further confirmed via genomic and cDNA sequencing in biparental and natural cucumber populations. Sequencing data showed that a 4-bp deletion was found in the sixth exon of Csa1G535800 in CGN19839, another inbred line, and there was also a mutation of an amino acid in Csa1G535800 that could contribute to the upward growth of pedicels in CGN19839. Moreover, it was found that Csa1G535800 exhibited strong expression in the pedicel of WT, suggesting its important role in development of pedicel orientation. Thus, Csa1G535800 was considered to be the candidate gene of CsUp. Conclusions CsUp encodes an Auxilin-like protein and controls pedicel orientation in cucumber. The identification of CsUp may help us to understand the mechanism of pedicel orientation development and allow for investigation of novel functions of Auxilin-like proteins in cucumber.

In cucumber (Cucumis sativus L.), the differentiation and development of female flowers are important processes that directly affect the fruit yield and quality. Sex differentiation is mainly controlled by three ethylene synthase genes, F (CsACS1G), M (CsACS2), and A (CsACS11). Thus, ethylene plays a key role in the sex differentiation in cucumber. The "one-hormone hypothesis" posits that F and M regulate the ethylene levels and initiate female flower development in cucumber. Nonetheless, the precise molecular mechanism of this process remains elusive. To investigate the mechanism by which F and M regulate the sex phenotype, three cucumber near-isogenic lines, namely H34 (FFmmAA, hermaphroditic), G12 (FFMMAA, gynoecious), and M12 (ffMMAA, monoecious), with different F and M loci were generated. The transcriptomic analysis of the apical shoots revealed that the expression of the B-class floral homeotic genes, CsPI (Csa4G358770) and CsAP3 (Csa3G865440), was immensely suppressed in G12 (100% female flowers) but highly expressed in M12 (∼90% male flowers). In contrast, CAG2 (Csa1G467100), which is an AG-like C-class floral homeotic gene, was specifically highly expressed in G12. Thus, the initiation of female flowers is likely to be caused by the downregulation of B-class and upregulation of C-class genes by ethylene production in the floral primordium. Additionally, CsERF31, which was highly expressed in G12, showed temporal and spatial expression patterns similar to those of M and responded to the ethylene-related chemical treatments. The biochemical experiments further demonstrated that CsERF31 could directly bind the promoter of M and promote its expression. Thus, CsERF31 responded to the ethylene signal derived from F and mediated the positive feedback regulation of ethylene by activating M expression, which offers an extended "one-hormone hypothesis" of sex differentiation in cucumber.

Light is an important environmental factor, which mainly inhibits hypocotyl elongation through various photoreceptors. In contrast, brassinosteroids (BRs) are major hypocotyl elongation-promoting hormones in plants, which could optimize photomorphogenesis concurrent with external light. However, the precise molecular mechanisms underlying the antagonism of light and BR signaling remain largely unknown. Here we show that the Arabidopsis red light receptor phyB is involved in inhibition of BR signaling via its direct interaction with the BR transcription factor BES1. In our study, the phyB mutant displays BR hypersensitivity, which is repressed in transgenic plants overexpressing phyB, suggesting that phyB negatively regulates the BR signaling pathway. In addition, protein interaction results show that phyB directly interacts with dephosphorylated BES1, the physiologically active form of BES1 induced by BR, in a red light-dependent manner. Genetic analyses suggest that phyB may act partially through BES1 to regulate BR signaling. Transcriptomic data and quantitative real-time PCR assay further show that phyB-mediated red light inhibits BR signaling by repressing expression of BES1 target genes, including the BR biosynthesis genes DWF4, the SAUR family and the PRE family genes required for promoting cell elongation. Finally, we found that red light treatment inhibits the DNA-binding activity of BES1 and photoactivated phyB represses the transcriptional activity of BES1 under red light. Taken together, we suggest that the interaction of phyB with dephosphorylated BES1 may allow plants to balance light and BR signaling by repressing transcriptional activity of BES1 to regulate expression of its target genes.

Light and the heterotrimeric G-protein are known to antagonistically regulate photomorphogenesis in Arabidopsis. However, whether light and G-protein coordinate the regulation of photomorphogenesis is largely unknown. Here we show that the blue light photoreceptor cryptochrome 1 (CRY1) physically interacts with the G-protein β subunit, AGB1, in a blue light-dependent manner. We also show that AGB1 directly interacts with HY5, a basic leucine zipper transcriptional factor that acts as a critical positive regulator of photomorphogenesis, to inhibit its DNA-binding activity. Genetic studies suggest that CRY1 acts partially through AGB1, and AGB1 acts partially through HY5 to regulate photomorphogenesis. Moreover, we demonstrate that blue light-triggered interaction of CRY1 with AGB1 promotes the dissociation of HY5 from AGB1. Our results suggest that the CRY1 signaling mechanism involves positive regulation of the DNA-binding activity of HY5 mediated by the CRY1–AGB1 interaction, which inhibits the association of AGB1 with HY5. We propose that the antagonistic regulation of HY5 DNA-binding activity by CRY1 and AGB1 may allow plants to balance light and G-protein signaling and optimize photomorphogenesis.

Proper timing of flowering is essential for reproduction of plants. Although it is well known that both light and gibberellin (GA) signaling play critical roles in promoting flowering in Arabidopsis thaliana, whether and how they are integrated to regulate flowering remain largely unknown. Here, we show through biochemical studies that DELLA proteins physically interact with CONSTANS (CO). Furthermore, the interaction of CO with NF-YB2 is inhibited by the DELLA protein, RGA. Our findings suggest that regulation of flowering by GA signaling in leaves under long days is mediated, at least in part, through repression of DELLA proteins on CO, providing a molecular link between DELLA proteins, key components in GA signaling pathway, and CO, a critical flowering activator in photoperiod signaling pathway.

Cryptochromes (CRY) are photolyase-like blue light receptors that mediate various light responses in plants and animals. In Arabidopsis, there are two homologous cryptochromes, CRY1 and CRY2, which mainly regulate photomorphogenesis and photoperiodic flowering, respectively (Guo et al., 1998; Lin et al., 1998). Cryptochromes are structurally divided into an N-terminal domain related to the photolyase and a C-terminal extension domain (Yang et al., 2000; Cashmore, 2003). The C-terminal domains of CRY1 and CRY2 (CCT1 [residues 490–681] and CCT2 [residues 486–612], also known as CCE1 and CCE2) are shown to mediate blue light signaling, whereas the N-terminal domains of CRY1 and CRY2 (CNT1 [residues 1–489] and CNT2 [residues 1–485]) are known to bind chromophores to sense blue light and mediate CRY dimerization (Yang et al., 2000; Brautigam et al., 2004; Sang et al., 2005).

Fundamental to plant and animal development is the regulated balance between cell proliferation and differentiation, a process intimately tied to cell cycle regulation. In Arabidopsis, mutations in TSO1, whose animal homolog is LIN54, resulted in severe developmental abnormalities both in shoot and root, including shoot meristem fasciation and reduced root meristematic zone. The molecular mechanism that could explain the tso1 mutant phenotype is absent. Through a genetic screen, we identified 32 suppressors that map to the MYB3R1 gene, encoding a conserved cell cycle regulator. Further analysis indicates that TSO1 transcriptionally represses MYB3R1, and the ectopic MYB3R1 activity mediates the tso1 mutant phenotype. Since animal homologs of TSO1 and MYB3R1 are components of a cell cycle regulatory complex, the DREAM complex, we tested and showed that TSO1 and MYB3R1 coimmunoprecipitated in tobacco leaf cells. Our work reveals a conserved cell cycle regulatory module, consisting of TSO1 and MYB3R1, for proper plant development.

Light is a key environmental cue that inhibits hypocotyl cell elongation through the blue and red/far-red light photoreceptors cryptochrome- and phytochrome-mediated pathways in Arabidopsis. In contrast, as a pivotal endogenous phytohormone auxin promotes hypocotyl elongation through the auxin receptors TIR1/AFBs-mediated degradation of AUX/IAA proteins (AUX/IAAs). However, the molecular mechanisms underlying the antagonistic interaction of light and auxin signaling remain unclear. Here, we report that light inhibits auxin signaling through stabilization of AUX/IAAs by blue and red light-dependent interactions of cryptochrome 1 (CRY1) and phytochrome B with AUX/IAAs, respectively. Blue light-triggered interactions of CRY1 with AUX/IAAs inhibit the associations of TIR1 with AUX/IAAs, leading to the repression of auxin-induced degradation of these proteins. Our results indicate that photoreceptors share AUX/IAAs with auxin receptors as the same direct downstream signaling components. We propose that antagonistic regulation of AUX/IAA protein stability by photoreceptors and auxin receptors allows plants to balance light and auxin signals to optimize their growth.

The characterization of straw decomposition and the resulting carbon (C) and nitrogen (N) release is crucial for understanding the effects of different straw returning methods on the immobilization and cycling of soil organic carbon (SOC) and soil total nitrogen (STN). In 2017&ndash, 2018, a field micro-plot experiment was carried out in northeastern China to investigate the effects of different straw returning approaches on straw decomposition, C release, N release, SOC, STN, and the soil C&ndash, N ratio. Six straw returning treatments were applied: straw mixed with soil (SM) and straw buried in the soil (SB) at soil depths of 10 (O), 30 (T), and 50 cm (F). The results indicate that the straw decomposition proportion (SD), C release, and N release in SM + O were higher than that in SM + T and SM + F. Moreover, SOC and STN concentrations and the soil C&ndash, N ratio were significantly enhanced by SM/B + O in the 0&ndash, 20 cm soil layers, SM/B + T in the 20&ndash, 30 cm soil layer, and SM/B + F in the 40&ndash, 60 cm soil layers. In the 0&ndash, 50 cm soil profile, the highest SOC stocks were obtained using SB + T. The STN stocks were also significantly affected by the straw returning depth, but the effect was inconsistent between the two years. SD had a positive relationship with SOC and STN in the 0&ndash, 20 cm soil layers, conversely, they were negatively related in the 30&ndash, 60 cm soil layers. The results of this study suggest that straw buried in the soil to a depth not exceeding 30 cm might be an optimal straw returning approach in northeastern China.

Eggplant is rich in anthocyanins, which are one of the important secondary metabolites and beneficial to human health. In this study, four anthocyanin biosynthesis genes, including chalcone synthase (SmCHS), chalcone isomerase (SmCHI), flavanone 3-hydroxylase (SmF3H) and dihydroflavonol 4-reductase (SmDFR), were isolated from eggplant. Their expression profiles were investigated along with other two structural genes (SmF3′5′H and SmANS) in different tissues, bagging, and low-temperature treatments. The highest expression levels were observed in peels except for SmF3H which was detected in stems, and SmF3H was also the exclusive gene that did not show correlation with anthocyanin content. Unlike purple peels of the control, the bagged fruits displayed white peels and had no anthocyanin accumulation, because of the expression of SmCHI, SmF3′5′H, SmDFR, and SmANS totally depended on light. As low temperature stimulates anthocyanin accumulation, all the six anthocyanin biosynthesis genes were up-regulated in cold stress experiment, and SmCHS increased most obviously. Moreover, early biosynthesis genes (SmCHS, SmCHI, and SmF3H) responded earlier than late biosynthesis genes (SmF3′5′H, SmDFR, and SmANS) under low temperature. Subcellular localization suggested that the enzymes encoded by the genes cloned in this study were all located in cytosol and nucleus. To further characterize the function, their ectopic expression in Arabidopsis was performed, and overexpression lines displayed higher anthocyanin accumulation in stems and siliques. The present study provides insight into anthocyanin biosynthesis in eggplant and may facilitate genetic engineering for improvement of the anthocyanin content in plants.