A mutation in SlCHLH encoding a magnesium chelatase H subunit is involved in the formation of yellow stigma in tomato (Solanum lycopersicum L.).

Chlorophylls are ubiquitous pigments responsible for the green color in plants. Changes in the chlorophyll content have a significant impact on photosynthesis, plant growth and development. In this study, we used a yellow stigma mutant (ys) generated from a green stigma tomato WT by using ethylmethylsulfone (EMS)-induced mutagenesis. Compared with WT, the stigma of ys shows low chlorophyll content and impaired chloroplast ultrastructure. Through map-based cloning, the ys gene is localized to a 100 kb region on chromosome 4 between dCAPS596 and dCAPS606. Gene expression analysis and nonsynonymous SNP determination identified the Solyc04g015750, as the potential candidate gene, which encodes a magnesium chelatase H subunit (CHLH). In ys mutant, a single base C to T substitution in the SlCHLH gene results in the conversion of Serine into Leucine (Ser92Leu) at the N-terminal region. The functional complementation test shows that the SlCHLH from WT can rescue the green stigma phenotype of ys. In contrast, knockdown of SlCHLH in green stigma tomato AC, observed the yellow stigma phenotype at the stigma development stage. Overexpression of the mutant gene Slys in green stigma tomato AC results in the light green stigma. These results indicate that the mutation of the N-terminal S92 to Leu in SlCHLH is the main reason for the formation of the yellow stigma phenotype. Characterization of the ys mutant enriches the current knowledge of the tomato chlorophyll mutant library and provides a novel and effective tool for understanding the function of CHLH in tomato.

The impact of attitude toward peer interaction on middle school students' problem-solving self-efficacy during the COVID-19 pandemic.

The outbreak of the COVID-19 epidemic has promoted the popularity of online learning, but has also exposed some problems, such as a lack of interaction, resulting in loneliness. Against this background, students' attitudes toward peer interaction may have become even more important. In order to explore the impact of attitude toward peer interaction on students' mindset including online learning motivation and critical thinking practice that could affect their problem-solving self-efficacy during the COVID-19 pandemic, we developed and administered a questionnaire, receiving 1,596 valid responses. The reliability and validity of the questionnaire were re-tested, and structural equation modeling was applied. It was found that attitude toward peer interaction could positively predict middle school students' online learning motivation and critical thinking. Learning motivation and critical thinking also positively supported problem-solving self-efficacy. It is expected that the results of this study can be a reference for teachers to adopt student-centered online learning in problem solving courses.

Supporting schools to use face recognition systems: a continuance intention perspective of elementary school parents in China.

A great deal of attention has been focused on technological innovation, for example, face recognition, which has been used in some countries in various fields. Nonetheless, there has been little attention paid to parents' acceptance of the use of face recognition systems on campus. To address this gap in the literature, this study examined how different degrees of technological innovativeness and dangerous beliefs in the virtual world (DBVW) influence parents' perceived value of using and intention to continue supporting schools' use of face recognition systems. This study adopted snowball sampling to collect data through questionnaires, and received 380 valid responses from parents living in Xuzhou, China. Confirmatory factor analysis and structural equation modeling were used to analyze the data, with results indicating that: (1) DBVW was negatively related to perceived value; (2) technological innovativeness was positively related to perceived value; and (3) perceived value was positively related to continuance intention to use face recognition systems. The results suggest that parents support the use of face recognition systems in elementary school; thus, such systems can be adopted by other elementary schools in other areas.

Identification of TALE Transcription Factor Family and Expression Patterns Related to Fruit Chloroplast Development in Tomato (Solanum lycopersicum L.).

The TALE gene family is an important transcription factor family that regulates meristem formation, organ morphogenesis, signal transduction, and fruit development. A total of 24 genes of the TALE family were identified and analyzed in tomato. The 24 SlTALE family members could be classified into five BELL subfamilies and four KNOX subfamilies. SlTALE genes were unevenly distributed on every tomato chromosome, lacked syntenic gene pairs, and had conserved structures but diverse regulatory functions. Promoter activity analysis showed that cis-elements responsive to light, phytohormone, developmental regulation, and environmental stress were enriched in the promoter of SlTALE genes, and the light response elements were the most abundant. An abundance of TF binding sites was also enriched in the promoter of SlTALE genes. Phenotype identification revealed that the green shoulder (GS) mutant fruits showed significantly enhanced chloroplast development and chlorophyll accumulation, and a significant increase of chlorophyll fluorescence parameters in the fruit shoulder region. Analysis of gene expression patterns indicated that six SlTALE genes were highly expressed in the GS fruit shoulder region, and four SlTALE genes were highly expressed in the parts with less-developed chloroplasts. The protein-protein interaction networks predicted interaction combinations among these SlTALE genes, especially between the BELL subfamilies and the KNOX subfamilies, indicating a complex regulatory network of these SlTALE genes in chloroplast development and green fruit shoulder formation. In conclusion, our result provides detailed knowledge of the SlTALE gene for functional research and the utilization of the TALE gene family in fruit quality improvement.

A new NLR gene for resistance to Tomato spotted wilt virus in tomato (Solanum lycopersicum).

KEY MESSAGE: A typical NLR gene, Sl5R-1, which regulates Tomato spotted wilt virus resistance, was fine mapped to a region less than 145 kb in the tomato genome. Tomato spotted wilt is a viral disease caused by Tomato spotted wilt virus (TSWV), which is a devastating disease that affects tomato (Solanum lycopersicum) production worldwide, and the resistance provided by the Sw-5 gene has broken down in some cases. In order to identify additional genes that confer resistance to TSWV, the F2 population was mapped using susceptible (M82) and resistant (H149) tomato lines. After 3 years of mapping, the main quantitative trait locus on chromosome 05 was narrowed to a genomic region of 145 kb and was subsequently identified by the F2 population, with 1971 plants in 2020. This region encompassed 14 candidate genes, and in it was found a gene cluster consisting of three genes (Sl5R-1, Sl5R-2, and Sl5R-3) that code for NBS-LRR proteins. The qRT-PCR and virus-induced gene silencing approach results confirmed that Sl5R-1 is a functional resistance gene for TSWV. Analysis of the Sl5R-1 promoter region revealed that there is a SlTGA9 transcription factor binding site caused by a base deletion in resistant plants, and its expression level was significantly up-regulated in infected resistant plants. Analysis of salicylic acid (SA) and jasmonic acid (JA) levels and the expression of SA- and JA-regulated genes suggest that SlTGA9 interacts or positively regulates Sl5R-1 to affect the SA- and JA-signaling pathways to resist TSWV. These results demonstrate that the identified Sl5R-1 gene regulates TSWV resistance by its own promoter interacting with the transcription factor SlTGA9.

SlCCD1A Enhances the Aroma Quality of Tomato Fruits by Promoting the Synthesis of Carotenoid-Derived Volatiles.

The loss of volatiles results in the deterioration of flavor in tomatoes. Volatiles are mainly derived from fatty acid, carotenoid, phenylpropane, and branched chain amino acids. In this study, the tomato accession CI1005 with a strong odor and accession TI4001 with a weak odor were analyzed. The volatile contents were measured in tomato fruits using gas chromatography-mass spectrometry. The scores of tomato taste and odor characteristics were evaluated according to hedonistic taste and olfaction. It was found that the content of fatty acid-derived volatiles accounted for more than half of the total volatiles that had grassy and fatty aromas. Phenylpropane-derived volatiles had irritation and floral aromas. Branched-chain amino acid-derived volatiles had a caramel aroma. Carotenoid-derived volatiles had floral, fruity, fatty, and sweet-like aromas, preferred by consumers. A lack of carotenoid-derived volatiles affected the flavor quality of tomato fruits. The accumulation of carotenoid-derived volatiles is regulated by carotenoid cleavage oxygenases (CCDs). A tissue-specific expression analysis of the SlCCD genes revealed that the expression levels of SlCCD1A and SlCCD1B were higher in tomato fruits than in other tissues. The expression levels of SlCCD1A and SlCCD1B were consistent with the trend of the carotenoid-derived volatile contents. The expression of SlCCD1A was higher than that for SlCCD1B. A bioinformatics analysis revealed that SlCCD1A was more closely linked to carotenoid metabolism than SlCCD1B. The overexpression of SlCCD1A indicated that it could cleave lycopene, α-carotene, and ß-carotene to produce 6-methyl-5-hepten-2-one, geranylacetone, α-ionone, and ß-ionone, increasing the floral, fruity, fatty, and sweet-like aromas of tomato fruits. The flavor quality of tomato fruits could be improved by overexpressing SlCCD1A.

Experimental and Analytical Study on Creep Characteristics of Box Section Bamboo-Steel Composite Columns under Long-Term Loading.

To expand the application of bamboo as a building material, a new type of box section composite column that combined bamboo and steel was considered in this paper. The creep characteristics of eight bamboo-steel composite columns with different parameters were tested to evaluate the effects of load level, section size and interface type under long-term loading. Then, the deformation development of the composite column under long-term loading was observed and analyzed. In addition, the creep-time relationship curve and the creep coefficient were created. Furthermore, the creep model of the composite column was proposed based on the relationship between the creep of the composite column and the creep of bamboo, and the calculated value of creep was compared with the experimental value. The experimental results showed that the creep development of the composite column was fast at first, and then became stable after about 90 days. The creep characteristics were mainly affected by long-term load level and section size. The creep coefficient was between 0.160 and 0.190. Moreover, the creep model proposed in this paper was applicable to predict the creep development of bamboo-steel composite columns. The calculation results were in good agreement with the experimental results.

Comparative Transcriptomic Analysis of the Development of Sepal Morphology in Tomato (Solanum Lycopersicum L.).

Sepal is an important component of the tomato flower and fruit that typically protects the flower in bud and functions as a support for petals and fruits. Moreover, sepal appearance influences the commercial property of tomato nowadays. However, the phenotype information and development mechanism of the natural variation of sepal morphology in the tomato is still largely unexplored. To study the developmental mechanism and to determine key genes related to downward sepal in the tomato, we compared the transcriptomes of sepals between downward sepal (dsp) mutation and the wild-type by RNA sequencing and found that the differentially expressed genes were dominantly related to cell expansion, auxin, gibberellins and cytokinin. dsp mutation affected cell size and auxin, and gibberellins and cytokinin contents in sepals. The results showed that cell enlargement or abnormal cell expansion in the adaxial part of sepals in dsp. As reported, auxin, gibberellins and cytokinin were important factors for cell expansion. Hence, dsp mutation regulated cell expansion to control sepal morphology, and auxin, gibberellins and cytokinin may mediate this process. One ARF gene and nine SAUR genes were dramatically upregulated in the sepal of the dsp mutant, whereas seven AUX/IAA genes were significantly downregulated in the sepal of dsp mutant. Further bioinformatic analyses implied that seven AUX/IAA genes might function as negative regulators, while one ARF gene and nine SAUR genes might serve as positive regulators of auxin signal transduction, thereby contributing to cell expansion in dsp sepal. Thus, our data suggest that 17 auxin-responsive genes are involved in downward sepal formation in the tomato. This study provides valuable information for dissecting the molecular mechanism of sepal morphology control in the tomato.

Mitigation of ammonia volatilization and nitrate leaching via loss control urea triggered H-bond forces.

Excess nitrogen (N) fertilizer applied to crops, which discharges to the environment, principally through denitrification, runoff, leaching, and volatilization, results in a waste of resources and pollution. Here, a high-performance loss control urea (LCU) was prepared by adding a loss control agent (LCA) with high thermal stability, large specific surface area, and good water retention capacity complex (6%) to traditional urea (94%). The existence of hydrogen bonds between LCA and N source for LCU in the presence of water enhanced N source adsorption capacity, where adsorption between LCA and NH4+-N was strongest, for urea and NO3--N was weakest. In a laboratory experiment, cumulative losses of NH3 volatilization from soils treated with N application rates of 80, 160 and 240 kg N ha-1 were 14.8, 18.1, and 24.2% for urea, respectively, and 10.1, 12.7, and 17.5% for LCU. Simulated rapid and long-term leaching experiments showed that, compared with urea, LCU reduced N leaching loss within 30 d, and delayed long-term N leaching loss. Hydrogen bonds in LCU effectively controlled NH3 volatilization and N leaching loss. This type of LCU may optimize supply of N in soils and increase adsorption and utilization of N in crops.

Overexpression of a Mitogen-Activated Protein Kinase SlMAPK3 Positively Regulates Tomato Tolerance to Cadmium and Drought Stress.

Mitogen-activated protein kinases (MAPKs) activation is a common defense response of plants to a range of abiotic stressors. SlMPK3, a serine-threonine protein kinase, has been reported as an important member of protein kinase cascade that also functions on plant stress tolerance. In this study, we cloned SlMPK3 from tomato and studied its role in cadmium (Cd2+) and drought tolerance. The results showed that transcripts of SlMAPK3 differentially accumulated in various plant tissues and were remarkably induced by different abiotic stressors and exogenous hormone treatments. Overexpression of SlMAPK3 increased tolerance to Cd2+ and drought as reflected by an increased germination rate and improved seedling growth. Furthermore, transgenic plants overexpressing SlMAPK3 showed an increased leaf chlorophyll content, root biomass accumulation and root activity under Cd2+ stress. Chlorophyll fluorescence analysis revealed that transgenic plants demonstrated an increased photosynthetic activity as well as contents of chlorophyll, proline, and sugar under drought stress. Notably, cadmium- and drought-induced oxidative stress was substantially attenuated in SlMAPK3 overexpressing plants as evidenced by lower malondialdehyde and hydrogen peroxide accumulation, and increased activity and transcript abundance of enzymatic antioxidants under stress conditions compared to that of wild-type. Our findings provide solid evidence that overexpression of SlMAPK3 gene in tomato positively regulates tolerance to Cd2+ and drought stress, which may have strengthen the molecular understanding of SlMAPK3 gene to improve abiotic stress tolerance.

Transcriptome Profiling of Tomato Uncovers an Involvement of Cytochrome P450s and Peroxidases in Stigma Color Formation.

Stigma is a crucial structure of female reproductive organ in plants. Stigma color is usually regarded as an important trait in variety identification in some species, but the molecular mechanism of stigma color formation remains elusive. Here, we characterized a tomato mutant, yellow stigma (ys), that shows yellow rather than typical green color in the stigma. Analysis of pigment contents revealed that the level of flavonoid naringenin chalcone was increased in the ys stigma, possibly as a result of higher accumulation of p-coumaric acid, suggesting that naringenin chalcone might play a vital role in yellow color control in tomato stigma. To understand the genes and gene networks that regulate tomato stigma color, RNA-sequencing (RNA-Seq) analyses were performed to compare the transcriptomes of stigmas between ys mutant and wild-type (WT). We obtained 507 differentially expressed genes, in which, 84 and 423 genes were significantly up-regulated and down-regulated in the ys mutant, respectively. Two cytochrome P450 genes, SlC3H1 and SlC3H2 which encode p-coumarate 3-hydroxylases, and six peroxidase genes were identified to be dramatically inhibited in the yellow stigma. Further bioinformatic and biochemical analyses implied that the repression of the two SlC3Hs and six PODs may indirectly lead to higher naringenin chalcone level through inhibiting lignin biosynthesis, thereby contributing to yellow coloration in tomato stigma. Thus, our data suggest that two SlC3Hs and six PODs are involved in yellow stigma formation. This study provides valuable information for dissecting the molecular mechanism of stigma color control in tomato. Statement: This study reveals that two cytochrome P450s (SlC3H1 and SlC3H2) and six peroxidases potentially regulate the yellow stigma formation by indirectly enhancing biosynthesis of yellow-colored naringenin chalcone in the stigma of tomato.

Transcriptomic Analysis Implies That GA Regulates Sex Expression via Ethylene-Dependent and Ethylene-Independent Pathways in Cucumber (Cucumis sativus L.).

Sex differentiation of flower buds is an important developmental process that directly affects fruit yield of cucumber (Cucumis sativus L.). Plant hormones, such as gibberellins (GAs) and ethylene can promote development of male and female flowers, respectively, however, the regulatory mechanisms of GA-induced male flower formation and potential involvement of ethylene in this process still remain unknown. In this study, to unravel the genes and gene networks involved in GA-regulated cucumber sexual development, we performed high throughout RNA-Seq analyses that compared the transcriptomes of shoot tips between GA3 treated and untreated gynoecious cucumber plants. Results showed that GA3 application markedly induced male flowers but decreased ethylene production in shoot tips. Furthermore, the transcript levels of M (CsACS2) gene, ethylene receptor CsETR1 and some ethylene-responsive transcription factors were dramatically changed after GA3 treatment, suggesting a potential involvement of ethylene in GA-regulated sex expression of cucumber. Interestingly, GA3 down-regulated transcript of a C-class floral homeotic gene, CAG2, indicating that GA may also influence cucumber sex determination through an ethylene-independent process. These results suggest a novel model for hormone-mediated sex differentiation and provide a theoretical basis for further dissection of the regulatory mechanism of male flower formation in cucumber. Statement: We reveal that GA can regulate sex expression of cucumber via an ethylene-dependent manner, and the M (CsACS2), CsETR1, and ERFs are probably involved in this process. Moreover, CAG2, a C-class floral homeotic gene, may also participate in GA-modulated cucumber sex determination, but this pathway is ethylene-independent.