Defective mutations in STAY-GREEN 1, PHYTOENE SYNTHASE 1, and MYB12 genes lead to formation of green ripe fruit in tomato.

Modern tomatoes produce colorful mature fruits, but many wild tomato ancestors form green or gray green ripe fruits. Here, tomato cultivar 'Lvbaoshi' (LBS) that produces green ripe fruits was found to contain three recessive loci responsible for fruit development. The colorless peel of LBS fruits was caused by a 603 bp deletion in the promoter of SlMYB12. The candidate genes of the remaining two loci were identified as STAY-GREEN 1 (SlSGR1) and PHYTOENE SYNTHASE 1 (SlPSY1). SGR1 and PSY1 co-suppression by RNAi converted the pink fruits into green ripe fruits in transgenic plants. An amino acid change in PSY1 and a deletion in the promoter of SGR1 were also identified in several wild tomatoes bearing green or gray ripe fruits. Overexpression of PSY1 from green ripe fruit wild tomatoes in LBS plants could only partially rescue the green ripe fruit phenotype of LBS, and transgenic lines expressing ProSGR1::SGR1 from Solanum pennellii also failed to convert purple-flesh into red-flesh fruits. This work uncovers a novel regulatory mechanism by which SlMYB12, SlPSY1, and SlSGR1 control fruit color in cultivated and some wild tomato species.

The tomato CONSTANS-LIKE protein SlCOL1 regulates fruit yield by repressing SFT gene expression.

BACKGROUND: CONSTANS (CO) and CONSTANS-LIKE (COL) transcription factors have been known to regulate a series of cellular processes including the transition from the vegetative growth to flower development in plants. However, their role in regulating fruit yield in tomato is poorly understood. RESULT: In this study, the tomato ortholog of Arabidopsis CONSTANS, SlCOL1, was shown to play key roles in the control of flower development and fruit yield. Suppression of SlCOL1 expression in tomato was found to lead to promotion of flower and fruit development, resulting in increased tomato fruit yield. On the contrary, overexpression of SlCOL1 disturbed flower and fruit development, and significantly reduced tomato fruit yield. Genetic and biochemical evidence indicated that SlCOL1 controls inflorescence development by directly binding to the promoter region of tomato inflorescence-associated gene SINGLE-FLOWER TRUSS (SFT) and negatively regulating its expression. Additionally, we found that SlCOL1 can also negatively regulate fruit size in tomato. CONCLUSIONS: Tomato SlCOL1 binds to the promoter of the SFT gene, down-regulates its expression, and plays a key role in reducing the fruit size.

A novel regulatory complex mediated by Lanata (Ln) controls multicellular trichome formation in tomato.

Trichomes that originate from plant aerial epidermis act as mechanical and chemical barriers against herbivores. Although several regulators have recently been identified, the regulatory pathway underlying multicellular trichome formation remains largely unknown in tomato. Here, we report a novel HD-ZIP IV transcription factor, Lanata (Ln), a missense mutation which caused the hairy phenotype. Biochemical analyses demonstrate that Ln separately interacts with two trichome regulators, Woolly (Wo) and Hair (H). Genetic and molecular evidence demonstrates that Ln directly regulates the expression of H. The interaction between Ln and Wo can increase trichome density by enhancing the expression of SlCycB2 and SlCycB3, which we previously showed are involved in tomato trichome formation. Furthermore, SlCycB2 represses the transactivation of the SlCycB3 gene by Ln and vice versa. Our findings provide new insights into the novel regulatory network controlling multicellular trichome formation in tomato.

Hair interacts with SlZFP8-like to regulate the initiation and elongation of trichomes by modulating SlZFP6 expression in tomato.

Trichomes are specialized glandular or non-glandular structures that provide physical or chemical protection against insect and pathogen attack. Trichomes in Arabidopsis have been extensively studied as typical non-glandular structures. By contrast, the molecular mechanism underlying glandular trichome formation and elongation remains largely unknown. We previously demonstrated that Hair is essential for the formation of type I and type VI trichomes. Here, we found that overexpression of Hair increased the density and length of tomato trichomes. Biochemical assays revealed that Hair physically interacts with its close homolog SlZFP8-like (SlZFP8L), and SlZFP8L also directly interacts with Woolly. SlZFP8L-overexpressing plants showed increased trichome density and length. We further found that the expression of SlZFP6, which encodes a C2H2 zinc finger protein, is positively regulated by Hair. Using chromatin immunoprecipitation, yeast one-hybrid, and dual-luciferase assays we identified that SlZFP6 is a direct target of Hair. Similar to Hair and SlZFP8L, the overexpression of SlZFP6 also increased the density and length of tomato trichomes. Taken together, our results suggest that Hair interacts with SlZFP8-like to regulate the initiation and elongation of trichomes by modulating SlZFP6 expression in tomato.

NF-Y plays essential roles in flavonoid biosynthesis by modulating histone modifications in tomato.

NF-Y transcription factors are reported to play diverse roles in a wide range of biological processes in plants. However, only a few active NF-Y complexes are known in plants and the precise functions of NF-Y complexes in flavonoid biosynthesis have not been determined. Using various molecular, genetic and biochemical approaches, we found that NF-YB8a, NF-YB8b and NF-YB8c - a NF-YB subgroup - can interact with a specific subgroup of NF-YC and then recruit either of two distinct NF-YAs to form NF-Y complexes that bind the CCAAT element in the CHS1 promoter. Furthermore, suppressing the expression of particular NF-YB genes increased the levels of H3K27me3 at the CHS1 locus and significantly suppressed the expression of CHS1 during tomato fruit ripening, which led to the development of pink-coloured fruit with colourless peels. Altogether, by demonstrating that NF-Y transcription factors play essential roles in flavonoid biosynthesis and by providing significant molecular insight into the regulatory mechanisms that drive the development of pink-coloured tomato fruit, we provide a major advance to our fundamental knowledge and information that has considerable practical value for horticulture.

miR156a-targeted SBP-Box transcription factor SlSPL13 regulates inflorescence morphogenesis by directly activating SFT in tomato.

The inflorescences and lateral branches of higher plants are generated by lateral meristems. The structure of the inflorescence has a direct effect on fruit yield in tomato (Solanum lycopersicum). We previously demonstrated that miR156a plays important roles in determining the structures of the inflorescences and lateral branches in tomato by suppressing the expression of the SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) transcription factor gene family. However, information on regulatory pathways associated with inflorescence morphogenesis is still lacking. In this study, we demonstrate that SPL13 is the major SPL involved in miR156a-regulated tomato inflorescence structure determination and lateral branch production. Suppressing the expression of SPL13 in tomato increases the number of inflorescences on vegetative branches and lateral branches, decreases the number of flowers and fruit, and reduces fruit size and yield. Genetic and biochemical evidence indicate that SPL13 controls inflorescence development by positively regulating the expression of the tomato inflorescence-associated gene SINGLE FLOWER TRUSS (SFT) by directly binding to its promoter region. Thus, our findings provide a major advance to our understanding of the miR156a-SlSPL-based mechanism that regulates plant architecture and yield in tomato.

Hair, encoding a single C2H2 zinc-finger protein, regulates multicellular trichome formation in tomato.

Trichomes originate from the epidermal cells of nearly all terrestrial plants, which are specialized unicellular or multicellular structures. Although the molecular mechanism regulating unicellular trichome formation has been extensively characterized, most of the genes essential for multicellular trichome formation remain unknown. In this study, we identified an associated locus on the long arm of chromosome 10 using a genome-wide association study (GWAS) on type-I trichomes of 180 diverse Solanum lycopersicum (tomato) accessions. Using map-based cloning we then cloned the key gene controlling the initiation of this type of trichome, named Hair (H), which encodes a single C2H2 zinc-finger protein. Transgenic experiments showed that hair-absent phenotype is caused by the deletion of the entire coding region of H. We identified three alleles of H containing several missense mutations and a nucleotide deletion, which result in amino acid substitutions and a reading frame shift, respectively. In addition, knockdown of H or Woolly (Wo) represses the formation of type-I trichomes, suggesting that both regulators may function as a heterodimer. Direct protein-protein interaction between them was further detected through pull-down and yeast two-hybrid assays. In addition, ectopic expression of H in Nicotiana tabacum (tobacco) and expression of its homologs from Capsicum annuum (pepper) and tobacco in tomato can trigger trichome formation. Taken together, these findings suggest that the H gene may be functionally conserved in multicellular trichome formation in Solanaceae species.

Ultrasonic Non-Destructive Detection Method for Residual Stress in Rotary Forging Aluminum Alloy Plates.

Aluminum alloy plates are widely used to manufacture large-scale integral structure parts in the field of aerospace. During the forming and processing of aluminum alloy plates, different degrees of residual stress are inevitably produced. Fast and accurate detection of residual stress is very essential to ensuring the quality of these plates. In this work, the longitudinal critically refracted (LCR) wave detection method based on a one-transmitter and double-receiver (OTDR) transducer and the finite element simulation were employed to obtain the residual stress. Aluminum alloy plates with different deformation amounts were fabricated by rotary forging to obtain different residual stress states. Results reveal that the plate formed by rotary forging is in a stress state of central tension and edge compression. As the deformation increases from 20% to 60%, the peak residual tensile stress increases from 156 MPa to 262 MPa, and there is no significant difference in the peak compressive stress. When the deformation reaches 60%, the difference in the residual stresses at different depths is less than 13%, which indicates that the plastic deformation zone basically penetrates the entire longitudinal cross-section of the plate. The maximum deviation between measurement and FE is 61 MPa, which means the experimental data are in good agreement with the FE results.

Pendular-Translational Hybrid Nanogenerator Harvesting Water Wave Energy.

Shore-based water wave energy produced by the impact of ocean waves on the coastline is a kind of clean and renewable energy. In this paper, a pendular-translational hybrid nanogenerator (PT-HNG) with two multilayer triboelectric nanogenerators and a spring base is proposed to harvest the wave energy. Pendular-translational movement mechanism is a sliding rail structure embedded with a permanent magnet, and the output is greatly improved compared to the previous pendular-pendular movement mechanism. Furthermore, the use of the spring base not only makes the device easy to install and fix but also increases the swing angle, which can better harvest the water wave energy. When the PT-HNG is used on the beach, a 33 µF capacitor can be charged to 4.3 V in 85 s. PT-HNG can be used to build self-powered wireless sensor networks to monitor the surrounding environment. This work proposes an innovative and efficient way to capture shore-based wave energy.

Tomato methionine sulfoxide reductase B2 functions in drought tolerance by promoting ROS scavenging and chlorophyll accumulation through interaction with Catalase 2 and RBCS3B.

Reactive oxygen species (ROS) are inevitably generated in aerobic organisms as by-products of common metabolism and as the result of defense and development. ROS readily oxidizes methionine (Met) residues of proteins to form Met-R-sulfoxide or Met-S-sulfoxide (MetSO), resulting in protein inactivation or malfunction. Although it is known that MetSO can be reverted to Met by methionine sulfoxide reductase (Msr), the mechanism how Msr interacts with its target proteins is poorly understood. In this study, two target proteins of tomato MsrB2 (SlMsrB2), catalase 2 (CAT2) and the Rubisco small subunit RBCS3B, were identified. Silencing of SlMsrB2 by RNA interference (RNAi) in tomato led to decreased drought tolerance, accompanied by increased ROS accumulation and chlorophyll degradation. By contrast, overexpression of SlMsrB2 in tomato significantly reduced ROS accumulation and enhanced drought tolerance. Protein interaction analysis showed that SlMsrB2 interacts with CAT2 and RBCS3B in vitro and in planta. Silencing of CAT2 by RNAi and RBCS3B by virus-induced gene silencing (VIGS) resulted in development of pale green leaves and enhanced ROS accumulation in tomato plants. These results demonstrate that SlMsrB2 functions in drought tolerance and promotes chlorophyll accumulation by modulating ROS accumulation.

Identification, genomic organization, and expression profiles of single C2H2 zinc finger transcription factors in tomato (Solanum lycopersicum).

C2H2 zinc finger proteins (ZFPs) play essential roles in leaf morphogenesis and floral development, as well as heat stress response and trichome formation, which activate or inhibit gene transcription mainly through interactions with nucleic acids, such as single-strand DNA, RNA binding or RNA/DNA bidirectional binding, and protein interaction. Single C2H2 ZFPs is the subfamily of ZFPs, but little of single C2H2 ZFP family is known in tomato. In this study, we identified 30 single ZFP genes in tomato using bioinformatics-based methods. Gene structures, phylogeny, conserved motifs, cis-element of promoter, chromosomal localization, gene duplication, and expression patterns of these single C2H2 ZFP genes were analyzed. Sequence analysis showed that most single C2H2 ZFP genes possessed only one exon, except for SlC1-liZFP1 and SlC1-liZFP2. These single C2H2 ZFP genes were asymmetrically distributed on 10 chromosomes, excluding 2 and 12 chromosomes. In addition, 24 of these genes were predicated to have experienced segmental duplication. Cis-element prediction indicated that many important elements were located in the putative promoter regions, like light and gibberellic acid (GA)-responsive elements. The expression profiles of these genes in different tissues and various hormones and stress treatment were further analyzed. Many genes were lowly expressed in all tissues, whereas some were specifically expressed in certain tissues, like SlC1-liZFP2 in young leaves, and SlC1-liZFP15 in fruits. Furthermore, these genes could also be induced by several hormones and stresses, including IAA, ETH, GA, cold, and drought. This study sets a good foundation for further characterizing the biological roles of single C2H2 ZFP genes in tomato.

Genome-wide identification, genomic organization and expression profiles of SlARR-B gene family in tomato.

The type-B authentic response regulators (ARR-Bs) function as positive regulators of cytokinin signal transduction and play important roles in abiotic stress resistance and plant development. However, little of ARR-B family is known in tomato. In this study, we performed a comprehensive analysis of ARR-B family factors in tomato. In total, 12 genes encoding ARR-B transcription factors (named as SlARR-B1-SlARR-B12) were identified from tomato. We analyzed the structures, chromosome locations, phylogeny, protein motifs, and expression profiles of these SlARR-B genes. Gene structure analysis showed that 5-12 exons and 4-11 introns existed in the SlARR-B genes. These SlARR-B genes were asymmetrically distributed on eight chromosomes in tomato. Phylogenetic tree of SlARR-B genes from tomato and other plant species revealed that SlARR-B genes were classified into 6 subfamilies. SlARR-B proteins had typical conserved domains, including Motif 1 and Motif 2. The investigation of the expression profiles of SlARR-B genes in all the examined tissues demonstrated that these genes were differentially expressed, including roots, stems, leaves, flowers, and fruits at developmental stages. Notably, the expression of SlARR-B11 and SlARR-B12 exhibited high expression levels in flowers. Each gene was induced by at least one of different phytohormones (SA, IAA, ABA, IBA, 6-BA, JA, GA, and ETH) and four abiotic stress treatments (heat, drought, salt, and cold). This study sets a good foundation for further characterization of the SlARR-B transcription factors in plant development and abiotic stress responses of tomato.