132 research outputs found
OTS1 and OTS2 SUMO proteases link plant development and survival under salt stress
No full textHigh salinity is an important factor limiting agriculture as major crops are salt sensitive. Understanding salt stress signalling is key to producing salt tolerant crops. The small ubiquitin-like modifier (SUMO) is a crucial regulator of signalling proteins in eukaryotes. Attachment of SUMO onto substrates is reversible and SUMO-proteases which specifically cleave the SUMO-substrate linkages play a vital regulatory role during SUMOylation. We have identified two SUMO proteases OTS1 and OTS2 that act redundantly to regulate salt stress responses in Arabidopsis. ots1 ots2 double mutants show extreme sensitivity to salt. However during non-salt conditions, ots1 ots2 double mutants are phenotypically similar to wild-type plants in terms of growth and development. Overexpressing SUMO1 in the ots1 ots2 double mutants severally diminishes plant size as quantified by rosette diameter even under non-stressed conditions. This reduction in plant growth is reminiscent of ots1 ots2 double mutants under salt stress. Our data indicates that overSUMOylation of target proteins can have severe effects on plant growth and that SUMO proteases like OTS1/2 are key to maintaining cellular balance of SUMOylation. We propose that upon environmental stress the hyperSUMOylation of key target proteins act to retard growth to survive stress periods. Addendum to: Conti L, Price G, O'Donnell E, Schwessinger B, Dominy P, Sadanandom A. Small ubiquitin-like modifier proteases OVERLY TOLERANT TO SALT1 and -2 regulate salt stress responses in Arabidopsis
A functional small ubiquitin-like modifier (SUMO) interacting motif (SIM) in the gibberellin hormone receptor GID1 is conserved in cereal crops and disrupting this motif does not abolish hormone dependency of the DELLA-GID1 interaction
No full textPlants survive adversity by modulating their growth in response to changing environmental signals. The phytohormone Gibberellic acid (GA) plays a central role in regulating these adaptive responses by stimulating the degradation of growth repressing DELLA proteins which accumulate during stress. The current model for GA signaling describes how this hormone binds to its receptor GID1 so promoting association of GID1 with DELLA, which then undergoes ubiquitin-mediated proteasomal degradation. Recent data revealed that conjugation of DELLAs to the Small Ubiquitin-like Modifier (SUMO) protein enables plants to modulate its abundance during environmental stress. This is achieved by SUMOylated DELLAs sequestering GID1 via its SUMO interacting motif (SIM) allowing non-SUMOylated DELLAs to accumulate leading to growth restraint under stress and potential yield loss. We demonstrate that GID1 proteins across the major cereal crops contain a functional SIM able to bind SUMO1. Site directed mutagenesis and yeast 2 hybrid experiments reveal that it is possible to disrupt the SIM-SUMO interaction motif without affecting the GA dependent DELLA–GID1 interaction and thereby uncoupling SUMO–mediated inhibition from DELLA degradation. Arabidopsis plants overexpressing a SIM mutant allele of GID1 perform better at relieving DELLA restraint than wild–type GID1. This evidence suggests that manipulating the SIM motif in the GA receptor may provide a possible route to developing stress tolerant crops plants
SUMO proteases OTS1 and 2 control filament elongation through a DELLA-dependent mechanism
No full textDuring fertilization, stamen elongation needs tobe synchronized with pistil growth. The phytohormonegibberellic acid (GA) promotes stamen growth by stimu-lating the degradation of growth repressing DELLA pro-teins. DELLA accumulation is negatively regulated byGAs through the ubiquitin–proteasome system. In Ara-bidopsis thaliana, a proportion of DELLAs is also conju-gated to the small ubiquitin-like modifier (SUMO) protein,which stabilizes DELLAs. Increased DELLA levels occurin the SUMO protease-deficient OVERLY TOLERANT TOSALT 1 and 2 (ots1 ots2 ) double mutants, especially undersalt stress conditions. Here, we show that OTS genes play aredundant role in the control of plant fertility under non-stress conditions. Mutants of ots1 ots2 display reducedfertility compared with the wild type, owing to reducedstamen elongation. Stamen growth, pollination rate andseed production are restored in ots1 ots2 della mutants,thus linking OTS1 function to the control of DELLAactivity in the context of filament elongation. OTS levelsappear to be developmentally regulated as OTS1/2 tran-script upregulation during stamen development overlapswith GAs accumulations. We propose that OTS genesenable synchronization of stamen development by facili-tating DELLA degradation at a specific developmentalstage
Small ubiquitin-like modifier protein SUMO enables plants to control growth independently of the phytohormone gibberellin
No full textPlants survive adverse conditions by modulating their growth in response to a changing environment. Gibberellins (GAs) play a key role in these adaptive responses by stimulating the degradation of growth-repressing DELLA proteins. GA binding to its receptor GID1 enables association of GID1 with DELLAs. This leads to the ubiquitin-mediated proteasomal degradation of DELLAs and consequently growth promotion. We report that DELLA-dependent growth control can be regulated independently of GA. We demonstrate that when a proportion of DELLAs is conjugated to the Small Ubiquitin-like Modifier (SUMO) protein, the extent of conjugation increases during stress. We identify a SUMO-interacting motif in GID1 and demonstrate that SUMO-conjugated DELLA binds to this motif in a GA-independent manner. The consequent sequestration of GID1 by SUMO-conjugated DELLAs leads to an accumulation of non-SUMOylated DELLAs, resulting in beneficial growth restraint during stress. We conclude that plants have developed a GA-independent mechanism to control growth
Small ubiquitin-like modifier proteases OVERLY TOLERANT TO SALT1 and -2 regulate salt stress responses in arabidopsis
No full textUnderstanding salt stress signaling is key to producing salt-tolerant crops. The small ubiquitin-like modifier (SUMO) is a crucial regulator of signaling proteins in eukaryotes. Attachment of SUMO onto substrates is reversible, and SUMO proteases, which specifically cleave the SUMO-substrate linkages, play a vital regulatory role during SUMOylation. We have identified two SUMO proteases, OVERLY TOLERANT TO SALT1 (OTS1) and OTS2, which are localized in the nucleus and act redundantly to regulate salt stress responses in Arabidopsis thaliana. ots1 ots2 double mutants show extreme sensitivity to salt. However, under low-salt conditions, ots1 ots2 double mutants are phenotypically similar to wild-type plants. We demonstrate that salt stress induces a dose-dependent accumulation of SUMO1/2-conjugated proteins in Arabidopsis. ots1 ots2 double mutants constitutively accumulate high levels of SUMO1/2-conjugated proteins even under nonstress conditions and show a further dramatic increase in SUMO1/2-conjugated proteins in response to salt stress. Transgenic lines overexpressing OTS1 have increased salt tolerance and a concomitant reduction in the levels of SUMOylated proteins. Conversely, the ectopic expression of the mutant ots1(C526S) protein lacking SUMO protease activity fails to produce a salt-tolerant phenotype. We show that salt directly affects OTS1-dependent signaling by inducing OTS1 protein degradation. Our results indicate a requirement for OTS1 deSUMOylation activity in plant salt tolerance response
The U-box protein AtPUB17 is a functional ortholog of NtACRE276 and its E3 ubiquitin ligase activity is required for plant cell death and defence
No full textPrevious analysis of transcriptional changes after elicitation of Cf-9-transgenic tobacco by Avr9 peptide revealed a rapidly upregulated gene NtACRE276. Here we show that NtACRE276 is transiently induced in leaves within 15 min by wounding, but upon Avr9 elicitor treatment this upregulation is further enhanced and maintained until the onset of cell death in Cf-9 tobacco. Silencing of NtACRE276 using RNAi in tobacco results in the loss of the hypersensitive response (HR) specified by Cf resistance genes. NtACRE276 RNAi plants are also compromised for HR mediated by the TMV defence elicitor, p50. Furthermore, silencing LeACRE276 in tomato leads to the breakdown of Cf-9-specified resistance against leaf mould caused by Cladosporium fulvum. We confirmed that NtACRE276 is an E3 ubiquitin ligase and that an intact U-box domain is required for this function. Bioinformatic analyses revealed that Arabidopsis PUB17 (AtPUB17) and Brassica napus ARC1 are the closest homologs of NtACRE276. Transiently expressing AtPUB17 in Cf-9 tobacco plants silenced for NtACRE276 leads to restoration of the HR whilst a mutant AtPUB17 lacking E3 ligase activity fails to do, demonstrating that the E3 ligase activity of AtPUB17 is crucial for defence signalling. AtPUB17 knockout plants are compromised in their RPM1- and RPS4-mediated resistance against Pseudomonas syringae pv. tomato containing avirulence genes AvrB and AvrRPS4, respectively. Our data identify the presence of a conserved class of U-box ARM repeat E3 ligases across the Solanaceous and Brassica genera that act as positive regulators of cell death and defence
Stability of small ubiquitin-like modifier (SUMO) proteases OVERLY TOLERANT TO SALT1 and -2 modulates salicylic acid signalling and SUMO1/2 conjugation inArabidopsis thaliana
No full textSmall ubiquitin-like modifier proteases 1 and 2 (SUMO1/2) have been linked to the regulation of salicylic acid (SA)-mediated defence signalling in Arabidopsis thaliana. In order to define the role of the SUMO proteases OVERLY TOLERANT TO SALT1 and -2 (OTS1/2) in defence and to provide insight into SUMO1/2-mediated regulation of SA signalling, we examined the status of SA-mediated defences in ots1/2 mutants. The ots1 ots2 double mutant displayed enhanced resistance to virulent Pseudomonas syringae and higher levels of SA compared with wild-type (WT) plants. Furthermore, ots1 ots2 mutants exhibited upregulated expression of the SA biosynthesis gene ICS1 in addition to enhanced SA-responsive ICS1 expression beyond that of WT. SA stimulated OTS1/2 degradation and promoted accumulation of SUMO1/2 conjugates. These results indicate that OTS1 and -2 act in a feedback loop in SA signalling and that de novo OTS1/2 synthesis works antagonistically to SA-promoted degradation, adjusting the abundance of OTS1/2 to moderate SA signalling. Accumulation of SUMO1/2 conjugates coincides with SA-promoted OTS degradation and may play a positive role in SA-mediated signalling in addition to its repressive roles reported elsewhere
Molecular regulation of protein repair in plants
No full textSIGLEAvailable from British Library Document Supply Centre-DSC:DXN023376 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
RAR1 and NDR1 contribute quantitatively to disease resistance in Arabidopsis, and their relative contributions are dependent on the R gene assayed
No full text- …
