Project description:The plant immune hormone salicylic acid (SA) modulates transcriptional reprogramming via controlling the master transcriptional coactivator, NPR1. Here we examined the role of HECT-type ubiquitin ligases, UPL1 and UPL5, in SA/NPR1-dependent transcriptional control. We showed that UPL1 and UPL5 are essential regulators of SA-responsive genes, and regulate SA-induced transcriptional reprogramming in a NPR1-dependent manner. Four-week old Arabidopsis thaliana plants of wild-type Col-0, mutant upl1, mutant upl5, and mutant npr1-1 genotypes were germinated on soil in 100% relative humidity. Plants were continuously grown in an environmental chamber with 16/8 hour day/night light regime (120 mol m-2 s-1 light intensity), 21/18 degrees celcius day/night cycle and 65% relative humidity. 4-week-old plants were sprayed with water or 0.5 mM SA until all leaves were thoroughly covered with fine droplets, samples were collected after 24 hours treatment. In total two independent biological repeats were collected.
Project description:Wounding is a trigger for both regeneration and defense in plants, but it is not clear if the two responses are linked by common activation or represent potential tradeoffs. While plant glutamate-like receptors (GLRs) are known to mediate defense responses, we implicate GLRs in regeneration through dynamic changes in chromatin and transcription in reprogramming cells near wound sites. Here, we show that genetic mutation and pharmacological inhibition of GLRs increases regeneration efficiency in multiple organ repair systems and plant species. Perturbation of GLR-mediated function, possibly by affecting Calcium fluxes, speeds cell division and re-specification of the stem cell niche while dampening a subset of defense responses. We show that the GLRs work through salicylic acid (SA) signaling in their effects on regeneration, with mutants in the SA receptor NPR1 partially resistant to GLR perturbation and hyper regenerative. These findings reveal a conserved mechanism that regulates a tradeoff between defense and regeneration and also offer new strategies to improve regeneration in agricultural and conservation.
Project description:The goal of the microarray experiment was to identify defense genes that were differentially expressed in the Arabidopsis mutants med16, med8, elp2, wild type in response to infection of the necrotrophic fungal pathogen Sclerotinia sclerotiorum. Results indicated that, compared with the wild type, the jasmonic acid (JA) biosynthesis genes LOX3, AOC3, and OPR3, ethylene (ET) biosynthesis genes ACS2 and ACS8, as well as salicylic acid (SA) biosynthesis genes ICS1 and EDS5 were up-regulated in med16 in local tissues at 1 day post-inoculation (dpi) and/or systemic tissues at 4 dpi. Surprisingly, however, while a number of SA pathway genes (EDS1, PAD4, NPR1, WRKY18, WRKY38, WRKY53, PR1, and PR2) and several JA-regulated wound-responsive genes (MYC2, JAR1, VSP1, and VSP2) were up-regulated in med16, a group of JA/ET-regulated defense genes (ORA59, ERF1, ERF14, PDF1.2, PDF1.2b, PDF1.2c, PDF1.3, PR4, and ChiB) and PR5 were down-regulated. On the other hand, only a few of these genes were differentially expressed between med8 or elp2 and the wild type.
Project description:Plant hormones involved in environmental stresses, namely abscisic acid (ABA), salicylic acid (SA), and jasmonic acid (JA), have been shown to interact with each other in a complex manner. To address the network of the hormone interactions, we have investigated the changes in expression under multiple hormone treatments, ABA+SA and ABA+JA. We chose cultured cells to remove the difference in the response to hormones among developmental cells or tissues. The cells were treated for 3hr and 24hr to see the rapid or transient response and steady-state response. The obtained data indicate that ABA and SA affect antagonistically, but these hormones affected many genes collaboratively. Indeed, according to the microarray data, there are many genes that responded only to ABA+SA. In addition, the ABA+SA responsive genes also responded to ABA+JA. These data suggest that hormone crosstalk is more complicated than expected and that more systematic analysis is required to untangle the hormone crosstalk network.
Project description:Salicylic acid (SA) and ethylene (ET) are two important plant hormones that regulate numerous plant growth, development, and stress response processes. Previous studies have suggested functional interplay of SA and ET in defense response, but precisely how these two hormones co-regulate plant growth and development processes remains unclear. The present findings reveal an antagonism between SA and ET in apical hook formation, a process that ensures successful soil emergence of dicotyledonous etiolated seedlings. Exogenous SA inhibited the ET-induced expression of HOOKLESS1 (HLS1) in a manner dependent on ETHYLENE INSENSITIVE3 (EIN3)/EIN3-LIKE1 (EIL1), the core transcription factors in the ET signaling pathway. We found that SA-activated NONEXPRESSER OF PR GENES1 (NPR1) physically interacted with EIN3 and interfered with the direct binding of EIN3 to target gene promoters, including the HLS1 promoter. Transcriptomic analysis further revealed that NPR1 and EIN3/EIL1 coordinately regulated subsets of genes that mediate plant growth and stress responses, suggesting that the interaction between NPR1 and EIN3/EIL1 might be an important mechanism for integrating the SA and ET signaling pathways in multiple physiological processes. Taken together, our findings shed light on the molecular mechanism underlying SA regulation of apical hook formation as well as the antagonism between SA and ET in early seedling establishment and possibly other physiological processes.
Project description:Activation of plant immunity is associated with dramatic transcriptome reprogramming to prioritise immune responses over normal cellular functions. Changes in gene expression are coordinated by the immune hormone salicylic acid (SA). Here we investigated the involvement of the E4 ubiquitin ligase UBE4/MUSE3 in SA-induced transcriptional reprogramming. We show that loss of UBE4 function results in amplified expression of SA-induced, NPR1-dependent gene expression. Twelve-day old Arabidopsis thaliana seedlings of wild-type Col-0, mutant ube4 (SAIL_713_A12) and mutant npr1-1 genotypes were grown on MS media supplemented with 1X Gamborg vitamins in an environmental chamber with 16/8 hour day/night light regime (120 mol m-2 s-1 light intensity) and 22 degrees Celcius. Seedlings were then transferred to 6-well plates and immersed in 10 ml of 0.5 mM SA or water. After 12 hours seedlings were harvested and for each treatment ~50 seedlings were pooled together into a single biological repeat. In total two independent biological repeats were collected. After harvesting seedlings were briefly dried on tissue and immediately frozen in liquid nitrogen until further analysis.