The MADS-Box Gene SlMBP21 Regulates Sepal Size Mediated by Ethylene and Auxin in Tomato.

Normal organ size is achieved by successful co-ordination of cell proliferation and cell expansion, which are modulated by multiple factors such as ethylene and auxin. In our work, SlMBP21-RNAi (RNA interference) tomato exhibited longer sepals and improved fruit set. Histological analysis indicated that longer sepals were attributed to cell expansion. To explore how SlMBP21 regulates sepal size, we compared the transcriptomes of sepals between SlMBP21-RNAi and the wild type by RNA sequencing and found that the differentially expressed genes were dominantly related to cell expansion, ethylene and auxin, and photosynthesis. Down-regulation of SlMBP21 affected ethylene production and the free IAA and IAA-Val intensity in sepals. Hormone treatment further indicated that SlMBP21 was involved in the ethylene and auxin pathways. As reported, ethylene and auxin were important factors for cell expansion. Hence, SlMBP21 negatively regulated cell expansion to control sepal size, and ethylene and auxin may mediate this process. Additionally, the contents of Chl and the activity of ribulose-1, 5-bisphosphate carboxylase/oxygenase, the key photosynthetic enzyme, were both increased in SlMBP21-RNAi sepals, which indicated that photosynthesis might be enhanced in transgenic longer sepals. Therefore, the longer sepal, with better protection and enhanced photosynthesis, may contribute to improve fruit set. Altogether, these results suggested that SlMBP21 was a novel factor involved in organ size control. Moreover, our study provided potential application value for improving fruit set.

Down-Regulation of SlGRAS10 in Tomato Confers Abiotic Stress Tolerance.

Adverse environmental factors like salt stress, drought, and extreme temperatures, cause damage to plant growth, development, and crop yield. GRAS transcription factors (TFs) have numerous functions in biological processes. Some studies have reported that the GRAS protein family plays significant functions in plant growth and development under abiotic stresses. In this study, we demonstrated the functional characterization of a tomato SlGRAS10 gene under abiotic stresses such as salt stress and drought. Down-regulation of SlGRAS10 by RNA interference (RNAi) produced dwarf plants with smaller leaves, internode lengths, and enhanced flavonoid accumulation. We studied the effects of abiotic stresses on RNAi and wild-type (WT) plants. Moreover, SlGRAS10-RNAi plants were more tolerant to abiotic stresses (salt, drought, and Abscisic acid) than the WT plants. Down-regulation of SlGRAS10 significantly enhanced the expressions of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) to reduce the effects of reactive oxygen species (ROS) such as O2- and H2O2. Malondialdehyde (MDA) and proline contents were remarkably high in SlGRAS10-RNAi plants. Furthermore, the expression levels of chlorophyll biosynthesis, flavonoid biosynthesis, and stress-related genes were also enhanced under abiotic stress conditions. Collectively, our conclusions emphasized the significant function of SlGRAS10 as a stress tolerate transcription factor in a certain variety of abiotic stress tolerance by enhancing osmotic potential, flavonoid biosynthesis, and ROS scavenging system in the tomato plant.

Overexpression of SlGRAS7 Affects Multiple Behaviors Leading to Confer Abiotic Stresses Tolerance and Impacts Gibberellin and Auxin Signaling in Tomato.

Abiotic stresses remain the key environmental issues that reduce plant development and therefore affect crop production. Transcription factors, such as the GRAS family, are involved in various functions of abiotic stresses and plant growth. The GRAS family of tomato (Solanum lycopersicum), SlGRAS7, is described in this study. We produced overexpressing SlGARS7 plants to learn more about the GRAS transcription factors. Plants overexpressing SlGARS7 (SlGRAS7-OE) showed multiple phenotypes related to many behaviors, including plant height, root and shoot length, and flowering time. We observed that many genes in the SlGRAS7-OE seedlings that are associated with auxin and gibberellin (GA) are downregulated and have altered sensitivity to GA3/IAA. SlGRAS7 was upregulated during abiotic stresses following treatment with sodium chloride (NaCl) and D-mannitol in the wild-type (WT) tomato. Tomato plants overexpressing SlGRAS7 showed more resistance to drought and salt stress comparison with WT. Our study of SlGRAS7 in tomato demonstrates how GRAS showed an integrative role, improving resistance to abiotic stresses and enhancing gibberellin/auxin signaling through reproductive as well as vegetative processes.

Genome-wide identification of the auxin/indole-3-acetic acid (Aux/IAA) gene family in pepper, its characterisation, and comprehensive expression profiling under environmental and phytohormones stress.

Auxin is an essential phytohormone that plays a crucial role in the growth and development of plants in stressful environments. Here, we analysed the auxin/indole-3-acetic acid (Aux/IAA) gene family, which produces auxin in pepper, and succeeded in identifying 27 putative members containing four conserved domains (I. II. III and IV) in their protein sequences. Sequence analysis, chromosomal mapping and motif prediction of all identified CaAux/IAA genes were performed. It was observed that these genes contained four conserved motifs divided into nine different groups and distributed across nine chromosomes in pepper plants. RNA-seq analysis revealed the organ specific expression of many CaAux/IAA genes. However, the majority of genes were expressed with high expression levels in the early stages of fruit development. However, the maximum expression level of the CA03g34540 gene was observed in the breaker stage. Moreover, thirteen CaAux/IAA genes were labelled as early responsive genes to various phytohormone and abiotic stresses. Furthermore, RNA-seq analysis in response to pathogen inoculation (PepMoV, TMV strains P0/P1, and Phytophthora capsici) showed distinct expression profiles of all identified genes, suggesting the diverse expression nature of genes under these stress conditions. Overall, this study provides insight into the dynamic response of CaAux/IAA genes under environmental and phytohormones stress conditions, providing bases to further explore the importance of these genes through mutant/transgenic analysis in pepper.

Genome-wide identification of FK506-binding domain protein gene family, its characterization, and expression analysis in tomato (Solanum lycopersicum L.).

FK506-protein also called FKBP protein belongs to PPIase (peptidylprolylcis-trans isomerase) super family of immune suppressive drugs that act as molecular protein chaperones. In plants, FKBPs are ubiquitous and involved in various biological and physiological processes like plant germination, development, stress response and hormonal signaling. Here, we identified 24 FKBP family genes in tomato by using different tools and bioinformatic approaches. The specific structure, domain organisation, cis-regulatory elements, phylogenetic analysis, multiple sequence alignment, tissue-specific expression patterns and expression under abiotic and phytohormone stresses of all genes were investigated. The genes are clustered on ten tomato chromosomes and are categorised into two sub-classes; single and multiple domains protein gene. One of the main features of tomato FKBPs is their large fractions localized in chloroplast (in silico analysis) and clustered together phylogenetically. Tissue-specific expression analysis using available RNA-seq data revealed the spatiotemporal expression of the FKBPs, but few genes were observed with relatively high expressions in certain developmental stages. However, the quantitative expression profile of all genes under hormone stress provided a supporting evidence for their potential role in hormone signal pathways. Our prediction not only providing the foundation for better understanding the complex physiological regulation of FKBP gene family in tomato but also providing the potential aids to accelerate tolerance and survival in tomato under stressful condition.

Functional Characterization of SlSAHH2 in Tomato Fruit Ripening.

S-adenosylhomocysteine hydrolase (SAHH) functions as an enzyme catalyzing the reversible hydrolysis of S-adenosylhomocysteine to homocysteine and adenosine. In the present work we have investigated its role in the ripening process of tomato fruit. Among the three SlSAHH genes we demonstrated that SlSAHH2 was highly accumulated during fruit ripening and strongly responded to ethylene treatment. Over-expression of SlSAHH2 enhanced SAHH enzymatic activity in tomato fruit development and ripening stages and resulted in a major phenotypic change of reduced ripening time from anthesis to breaker. Consistent with this, the content of lycopene was higher in SlSAHH2 over-expression lines than in wild-type at the same developmental stage. The expression of two ethylene inducible genes (E4 and E8) and three ethylene biosynthesis genes (SlACO1, SlACO3 and SlACS2) increased to a higher level in SlSAHH2 over-expression lines at breaker stage, and one transgenic line even produced much more ethylene than wild-type. Although inconsistency in gene expression and ethylene production existed between the two transgenic lines, the transcriptional changes of several important ripening regulators such as RIN, AP2a, TAGL1, CNR and NOR showed a consistent pattern. It was speculated that the influence of SlSAHH2 on ethylene production was downstream of the regulation of SlSAHH2 on these ripening regulator genes. The over-expressing lines displayed higher sensitivity to ethylene in both fruit and non-fruit tissues. Ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) treatment accelerated ripening faster in SlSAHH2 over-expressing fruit than in wild-type. Additionally, seedlings of transgenic lines displayed shorter hypocotyls and roots in ethylene triple response assay. In conclusion, SlSAHH2 played an important role in tomato fruit ripening.