Tomato Lateral Root Research Articles

A GARP transcription factor SlGCC positively regulates lateral root development in tomato via auxin-ethylene interplay.

SlGCC, a GARP transcription factor, functions as a root-related transcriptional repressor. SlGCC synchronizes auxin and ethylene signaling involving SlPIN3 and SlIAA3 as intermediate targets sketching a molecular map for lateral root development in tomato. The root system is crucial for growth and development of plants as it performs basic functions such as providing mechanical support, nutrients and water uptake, pathogen resistance and responds to various stresses. SlGCC, a GARP family transcription factor (TF), exhibited predominant expression in age-dependent (initial to mature stages) tomato root. SlGCC is a transcriptional repressor and is regulated at a transcriptional and translational level by auxin and ethylene. Auxin and ethylene mediated SlGCC protein stability is governed via proteasome degradation pathway during lateral root (LR) growth development. SlGCC over-expressor (OE) and under-expressed (UE) tomato transgenic lines demonstrate its role in LR development. This study is an attempt to unravel the vital role of SlGCC in regulating tomato LR architecture.

Glutathione produced by γ-glutamyl cysteine synthetase acts downstream of hydrogen to positively influence lateral root branching

Hydrogen gas (H2) mediation of lateral root (LR) branching was previously described.However, related signaling pathway is largely unexplored. In this study, we discovered that application with H2 using hydrogen-rich water, mimicking the responses of exogenous glutathione (GSH), not only enhanced GSH synthesis, but also induced tomato LR development. The changes in the transcripts of auxin signaling-related genes and cell cycle regulatory genes were matched with above phenotypes. The addition of H2 could trigger higher transcript levels of SlGSH1 and SlGSH2, encoding γ-glutamylcysteine synthetase (γ-ECS) and glutathione synthetase (GS), confirming the stimulation of GSH synthesis. These responses were greatly abolished when the inhibitor of γ-ECS was applied. The inhibition in lateral root primordium development, especially in emergence stage, was also observed. Genetic evidence revealed that the defects in GSH production and lateral rooting in Arabidopsis cad2-1, a γ-ECS defective mutant, were obviously abolished in the presence of GSH compared to those in the presence of H2. Further evidence revealed that mRNA levels of target genes elicited by H2 in wild-type, were differentially impaired in mutant plants. Together, above data clearly demonstrated that γ-ECS-dependent GSH production might be closely associated with H2 control of LR branching.

Hydrogen peroxide is involved in methane-induced tomato lateral root formation.

Pharmacological and molecular evidence reveals a novel role of methane (CH4) gas in root organogenesis, the induction of lateral root (LR) formation, and this response might require hydrogen peroxide (H2O2) synthesis. Although plants can produce CH4 and release this to atmosphere, the beneficial role(s) of CH4 are not fully elucidated. In this study, the fumigation with CH4 not only increased NADPH oxidase activity and H2O2 production, but also induced tomato lateral root primordial formation and thereafter LR development. However, exogenously applied argon and nitrogen failed to influence LR formation. Above responses triggered by CH4 were sensitive to the removal of endogenous H2O2 with dimethylthiourea (DMTU; a membrane-permeable scavenger of H2O2), suggesting the hypothesis that CH4's effect on LR formation could be mediated by endogenous H2O2. Diphenylene iodonium (DPI) inhibition of the H2O2 generating enzyme NADPH oxidase attenuated H2O2 synthesis and impaired LR formation in response to CH4, confirming the requirement of NADPH oxidase-dependent H2O2. Meanwhile, the alterations of endogenous H2O2 concentrations failed to influence CH4 production in tomato seedlings. Molecular evidence revealed that CH4-induced SlCDKA1, SlCYCA2;1, and SlCYCA3;1 transcripts, and -decreased SlKRP2 mRNA were impaired by DMTU or DPI. Contrasting changes in LR formation-related miR390a and miR160 transcripts and their target genes, including SlARF4 and SlARF16, were observed. Together, our pharmacological and molecular evidence suggested the requirement of H2O2 synthesis in CH4-triggered tomato LR formation, partially via the regulation of cell cycle regulatory genes, miRNA-, and tasiRNA-modulated gene expression.

Over-expression of Peach PpIAA19 in Tomato Alters Plant Growth, Parthenocarpy, and Fruit Shape

The auxin/indole acetic acid (Aux/IAA) genes encode a large family of short-lived proteins that regulate auxin signaling in plants. Previous attempts to understand the role of auxin during fruit development in peach (Prunus persica) found that expression of the Aux/IAA gene PpIAA19 was upregulated during fruit ripening, but the biological significance of the PpIAA19 protein is still unknown. The current study detected PpIAA19 transcripts in all peach plant tissues but found higher levels of accumulation in fruit S1 and S4II stages. During fruit ripening, the expression level of the PpIAA19 gene in melting flesh (MF) peach fruit was unsurprisingly higher than in stony hard (SH) peach fruit. Tomato (Solanum lycopersicum cv. ‘Micro-Tom’) was used as a model for investigating the phenotypic and molecular changes associated with over-expression of PpIAA19. This revealed that PpIAA19 was involved in regulating tomato lateral root number, stem elongation, parthenocarpy, and fruit shape. Molecular analyses of transgenic tomato plants over-expressing PpIAA19 indicated that the observed phenotypic changes were partially mediated by regulating the expression of auxin response genes. This result extends the functional characterization of PpIAA19 in tomato, and broadens our understanding of the role of auxin signaling in regulating plant growth and development.

Hydrogen peroxide is involved in hydrogen sulfide-induced lateral root formation in tomato seedlings

BackgroundBoth hydrogen sulfide (H2S) and hydrogen peroxide (H2O2) are separately regarded as a highly reactive molecule involved in root morphogenesis. In this report, corresponding causal link governing lateral root formation was investigated.MethodsBy using pharmacological, anatomic, and molecular approaches, evidence presented here revealed the molecular mechanism underlying tomato lateral root development triggered by H2S.ResultsA H2S donor sodium hydrosulfide (NaHS) triggered the accumulation of H2O2, the up-regulation of RBOH1 transcript, and thereafter tomato lateral root formation. Above responses were sensitive to the H2O2 scavenger (dimethylthiourea; DMTU) and the inhibitor of NADPH oxidase (diphenylene idonium; DPI), showing that the accumulations of H2O2 and increased RBOH1 transcript were respectively prevented. Lateral root primordial and lateral root formation were also impaired. Further molecular evidence revealed that H2S-modulated gene expression of cell cycle regulatory genes, including up-regulation of SlCYCA2;1, SlCYCA3;1, and SlCDKA1, and the down-regulation of SlKRP2, were prevented by the co-treatment with DMTU or DPI. Above mentioned inducing phenotypes were consistent with the changes of lateral root formation-related microRNA transcripts: up-regulation of miR390a and miR160, and with the opposite tendencies of their target genes (encoding auxin response factors). Contrasting tendencies were observed when DMTU or DPI was added together. The occurrence of H2S-mediated S-sulfhydration during above responses was preliminarily discovered.ConclusionsOverall, these results suggested an important role of RBOH1-mediated H2O2 in H2S-elicited tomato lateral root development, and corresponding H2S-target proteins regulated at transcriptional and post-translational levels.

Hydrogen Peroxide Is Involved in β-Cyclodextrin-hemin Complex-Induced Lateral Root Formation in Tomato Seedlings.

Although previous results showed that β-cyclodextrin-hemin complex (β-CDH) could induce tomato lateral root (LR) formation, the corresponding downstream messengers are still not fully understood. In this report, similar to the inducing effects of exogenously applied hydrogen peroxide (H2O2), we discovered that β-CDH elicited RBOH1 transcript upregulation, endogenous H2O2 accumulation, and thereafter tomato LR development. Above responses were sensitive to dimethylthiourea (DMTU) and ascorbic acid (AsA), two membrane-permeable scavengers of H2O2, showing that accumulation of H2O2 and LR formation were significantly blocked. The test with diphenyleneiodonium (DPI; the inhibitor of NADPH oxidase) revealed that H2O2 mainly produced by NADPH oxidase, might be involved in LR formation triggered by β-CDH. qPCR combined with pharmacological and anatomical analyses showed that β-CDH-modulated several marker genes responsible for LR formation, such as CYCA3;1, CYCA2;1, CYCD3;1, and CDKA1 (four cell cycle regulatory genes), ARF7 and RSI-1 (two auxin signaling genes), LAX3 (an auxin influx carrier), IAA14 (encoding a member of the Aux/IAA protein family), PIN3 and PIN7 (two auxin efflux carriers), isocitrate dehydrogenase [NADP], NADH-cytochrome b5 reductase 1, and L-ascorbate oxidase homolog genes (two reactive oxygen species-associated genes and one LR formation-related gene), were causally related to above H2O2 signaling. Particularly, representative proteins related to H2O2 metabolism and lateral rooting, were specifically induced in β-CDH-treated tomato seedlings. Overall, the results clearly suggested a vital role of H2O2 in the β-CDH-induced tomato LR formation, and β-CDH-elicited H2O2-related target proteins responsible for LR formation might be, at least partially, regulated at transcriptional and translational levels.

Involvement of glutathione in β-cyclodextrin-hemin complex-induced lateral root formation in tomato seedlings

β-cyclodextrin-hemin complex (β-CDH) was shown to induce lateral root (LR) formation in tomato. However, the molecular mechanism is still elusive. In this report, the role of reduced glutathione (GSH) in the induction of lateral root triggered by β-CDH was investigated. Similar to the responses of β-CDH, exogenously applied with 0.1 mο GSH not only increased endogenous GSH content determined by spectrophotography and the monochlorobimane (MCB)-dependent fluorescent analysis, but also induced, thereafter, LR formation. Meanwhile, both β-CDH- and GSH-induced lateral root primordia (LRP) exhibited a similar accelerated anatomic structure. Above inducible responses were blocked significantly when the L-buthionine-(S,R)-sulfoximine (BSO), a potent and specific inhibitor of the enzyme catalyzing the first step of GSH biosynthesis, was separately applied. Upon β-CDH treatment, the changes of endogenous GSH content determined by spectrophotography and fluorescent analysis were consistent with the transcripts of two GSH synthetic genes, GSH1 and GSH2 encoding γ-glutamyl cysteine synthetase and glutathione synthetase, respectively. Exogenously applied with β-CDH could rescue N-1-naphthylphthalamic acid (NPA; IAA depletion)-triggered inhibition of LR formation. Further molecular evidence revealed that both β-CDH and GSH modulated gene expression of cell cycle regulatory genes (CYCA2;1, CYCA3;1, CYCD3;1, and CDKA1) and auxin signaling genes (ARF7 and RSI-1), six marker genes responsible for LR formation. By contrast, above changes were sensitive to the co-treatment with BSO. All together, these results suggest a role for GSH in the regulation of tomato LR development triggered by β-CDH.

β-Cyclodextrin-hemin complex-induced lateral root formation in tomato: involvement of nitric oxide and heme oxygenase 1.

β-Cyclodextrin-hemin complex-induced tomato lateral root formation was associated with nitric oxide and heme oxygenase 1 by modulating cell cycle regulatory genes. β-Cyclodextrin-hemin complex (β-CDH), a complex by combining β-cyclodextrin (β-CD) with hemin, a heme oxygenase 1 (HO1) inducer, was a trigger of cucumber adventitious root formation by enhancing HO1 gene expression. In this report, our results identified the previously unknown function of β-CDH in plants: the inducer of tomato lateral root (LR) formation. β-CDH-triggered LR formation is hemin-specific, since β-CD failed to induce LR development. Because nitric oxide (NO) is involved in LR formation, the correlation of β-CDH with NO and HO1 was investigated. Our analysis suggested that β-CDH induced an increase in endogenous NO production, followed by up-regulation of tomato HO1 gene and LR formation, all of which were mimicked by hemin and two NO-releasing compounds (SNP and GSNO). The induction of HO1 gene expression and LR formation triggered by β-CDH or hemin were significantly blocked by an inhibitor of HO1. Further results revealed that both β-CDH- and SNP-stimulated HO1 gene expression and thereafter LR formation were sensitive to the removal of NO with a potent NO scavenger, and the responses of SNP were significantly blocked by an inhibitor of HO1. Molecular evidence illustrated that representative cell cycle regulatory genes, including SlCDKA1, SlCYCA3;1, SlCYCA2;1, and SlCYCD3;1, were significantly up-regulated by β-CDH and SNP, but obviously blocked when seedlings were co-treated with the scavenger of NO or the inhibitor of HO1. In summary, our physiological and molecular evidence demonstrated that both NO and HO1 were involved in the β-CDH-induced LR formation with, at least partially, HO1 acting downstream of NO signaling.

The anthocyanin reduced tomato mutant demonstrates the role of flavonols in tomato lateral root and root hair development.

This study utilized tomato (Solanum lycopersicum) mutants with altered flavonoid biosynthesis to understand the impact of these metabolites on root development. The mutant anthocyanin reduced (are) has a mutation in the gene encoding FLAVONOID 3-HYDROXYLASE (F3H), the first step in flavonol synthesis, and accumulates higher concentrations of the F3H substrate, naringenin, and lower levels of the downstream products kaempferol, quercetin, myricetin, and anthocyanins, than the wild type. Complementation of are with the p35S:F3H transgene reduced naringenin and increased flavonols to wild-type levels. The initiation of lateral roots is reduced in are, and p35S:F3H complementation restores wild-type root formation. The flavonoid mutant anthocyanin without has a defect in the gene encoding DIHYDROFLAVONOL REDUCTASE, resulting in elevated flavonols and the absence of anthocyanins and displays increased lateral root formation. These results are consistent with a positive role of flavonols in lateral root formation. The are mutant has increased indole-3-acetic acid transport and greater sensitivity to the inhibitory effect of the auxin transport inhibitor naphthylphthalamic acid on lateral root formation. Expression of the auxin-induced reporter (DR5-β-glucuronidase) is reduced in initiating lateral roots and increased in primary root tips of are. Levels of reactive oxygen species are elevated in are root epidermal tissues and root hairs, and are forms more root hairs, consistent with a role of flavonols as antioxidants that modulate root hair formation. Together, these experiments identify positive roles of flavonols in the formation of lateral roots and negative roles in the formation of root hairs through the modulation of auxin transport and reactive oxygen species, respectively.

Heme oxygenase-1 is involved in sodium hydrosulfide-induced lateral root formation in tomato seedlings

By using pharmacological and molecular approaches, we discovered the involvement of HO-1 in NaHS-induced lateral root formation in tomato seedlings. Heme oxygenase-1 (HO-1) and hydrogen sulfide (H2S) regulate various responses to abiotic stress and root development, but their involvement in the simultaneous regulation of plant lateral root (LR) formation is poorly understood. In this report, we observed that the exogenously applied H2S donor sodium hydrosulfide (NaHS) and the HO-1 inducer hemin induce LR formation in tomato seedlings by triggering intracellular signaling events involving the induction of tomato HO-1 (SlHO-1), and the modulation of cell cycle regulatory genes, including the up-regulation of SlCDKA;1 and SlCYCA2;1, and simultaneous down-regulation of SlKRP2. The response of NaHS in the induction of LR formation was impaired by the potent inhibition of HO-1, which was further blocked when 50 % saturation of carbon monoxide (CO) aqueous solution, one of the catalytic by-products of HO-1, was added. Further molecular evidence revealed that the NaHS-modulated gene expression of cell cycle regulatory genes was sensitive to the inhibition of HO-1 and reversed by cotreatment with CO. The impairment of LR density and length as well as lateral root primordia number, the decreased tomato HO-1 gene expression and HO activity caused by an H2S scavenger hypotaurine were partially rescued by the addition of NaHS, hemin and CO (in particular). Together, these results revealed that at least in our experimental conditions, HO-1 might be involved in NaHS-induced tomato LR formation. Additionally, the use of NaHS and hemin compounds in crop root organogenesis should be explored.

Involvement of haem oxygenase-1 in hydrogen peroxide-induced lateral root formation in tomato

The objective of this study was to test whether haem oxygenase-1 (HO-1) is involved in hydrogen peroxide (H2O2)-induced lateral root (LR) formation. The results showed that 0.1 mM H2O2 mimicked the effects of the HO-1 inducer, haemin, on the up-regulation of tomato HO-1 (SlHO1) expression, increased carbon monoxide (CO) synthesis and LR formation. However, 1.0 mM H2O2 resulted in inhibitory responses. The above inducible or inhibitory responses elicited by 0.1 and 1.0 mM H2O2 were noticeably blocked or rescued by the HO-1 inhibitor zinc protoporphyrin IX (ZnPP) or haemin, and then separately reversed by CO or ZnPP. Further trials showed that haemin-induced responses were not altered by the H2O2 trap, dimethylthiourea (DMTU). When applied alone, DMTU not only decreased H2O2 contents but also inhibited SlHO1 expression and LR development. These responses were recovered by the application of haemin or CO. Molecular evidence revealed that H2O2-modulated expression of the target genes responsible for LR formation was blocked by ZnPP, but rescued by CO. Salinity-induced up-regulation of HO-1 expression and thereafter LR formation were also dependent on the H2O2 generation. Overall, these results demonstrated a possible role of HO-1 in the H2O2-induced tomato LR formation.

Altered Expression of MicroRNAs and Target mRNAs in Tomato Root and Stem Tissues upon Different Viral Infection

AbstractMicroRNAs (miRNAs) are post‐transcriptional regulators that are involved in numerous biological processes in both plants and animals. In plants, root and stem tissues play essential roles in their anchorage to soil as well as in nutrient and water uptake and transfer. We have quantified the expression alterations of eleven miRNAs and their target mRNAs in tomato root and stem tissues after infection with Cucumber mosaic virus (CMV)‐Fny, CMV‐FnyΔ2b (a CMV‐Fny 2b‐deletion mutant), CMV‐Fny‐satT1 (CMV‐Fny plus an aggressive satellite (sat) RNA variant satT1) and Tomato aspermy virus (TAV)‐Bj. From 21 days postinoculation onwards, we found the stem tissues were ‘hollow’ in CMV‐Fny‐satT1 infected tomatoes, and a ‘fibrosis’ phenotype was observed in stems of TAV‐Bj infected plants. In addition, this phenotype was associated with the decreasing of tomato lateral root numbers upon the two infections. Consistence with these phenotypic alterations, tomato miRNA/mRNA levels upon different viral infections were changed by different degrees. Based on our results, the interference of different viral infections with tomato miRNA pathways were analysed and the correlations between miRNAs/mRNAs expression alterations and tomato symptoms were discussed.

Heme oxygenase is involved in cobalt chloride-induced lateral root development in tomato

In animals, heme oxygenase (HO), a rate-limiting enzyme responsible for carbon monoxide (CO) production, was regarded as a protective system maintaining cellular homeostasis. It was also established that metal ions are powerful HO-inducing agents and cobalt chloride (CoCl(2)) was the first metal ion identified with an inducing property. Previous study suggests that CoCl(2) stimulates adventitious root formation in tomato and cucumber cuttings. In this test, we discover that both CoCl(2) and an inducer of HO-1, hemin, could lead to the promotion of lateral root development, as well as the induction of HO-1 protein expression, HO activity, or LeHO-1/2 transcripts, in lateral root initiation zone of tomato seedlings. The effect is specific for HO since the potent HO-1 inhibitor zinc protoporphyrin IX (ZnPPIX) blocked the above actions of CoCl(2), and the inhibitory effect was reversed partially when 50% CO aqueous solution was added. However, the addition of ascorbic acid (AsA), a well-known antioxidant, exhibited no obvious effect on lateral root formation. Molecular evidence further showed that CoCl(2)-induced the up-regulation of target genes responsible for lateral root formation, including LeCDKA1, LeCYCA2;1, and LeCYCA3;1, was suppressed differentially by ZnPPIX. And these decreases were reversed further by the addition of CO. All together, these results suggest a novel role for HO in the CoCl(2)-induced tomato lateral root formation.

Regulation of tomato lateral root development by carbon monoxide and involvement in auxin and nitric oxide

Carbon monoxide (CO) is an endogenous gaseous molecule in organisms. Despite its reputation as a lethal gas, recent studies have shown that it is one of the most essential cellular components regulating a variety of biological processes. However, whether CO regulates physiological processes of morphological or developmental patterns in plants is largely unknown. In this paper, the observation that exogenous CO was able to promote the formation of tomato lateral roots (LR) is described. The CO stimulation of LR development was supported by analysis of tomato haem oxygenase-1 (LeHO-1), an enzymatic source of intracellular CO. It is shown that the amount of LeHO-1 proteins and transcripts increased parallel to the LR development. In addition, LeHO-1 loss-of-function tomato mutant yg-2 showed a phenotype of impaired LR development. The phenotype of yg-2 could be restored by treatment with CO. Since auxin is required for LR initiation and NO is shown to be a mediator for LR development, the correlation of CO with auxin and NO was tested. Our analysis revealed that the action of CO was blocked by the auxin transport inhibitor N-1-naphthylphthalamic acid and the NO scavenger cPTIO, respectively. Furthermore, the whole seedling assays of IAA show that treatment with CO increased the overall IAA levels in various tissues of tomato. Exposure of tomato roots to CO also enhanced intracellular NO generation. These results indicate that CO plays a critical role in controlling architectural change in tomato roots.

Analysis of Tomato Root Initiation Using a Normal Mixture Distribution

We attempt to identify the number of underlying physical phenomena behind tomato lateral root initiation by using a normal mixture distribution coupled with the Box-Cox power transformation. An initial analysis of the data suggested the possibility of two (possibly more) subpopulations, but upon taking reciprocals, the data appear to be very nearly Gaussian. A simulation study explores the possibility of erroneously detecting a second subpopulation by fitting data which are improperly scaled. A power calculation suggests that only unrealistically large sample sizes can detect the unbalanced mixtures one might expect with data of this type.