Redundant CAMTA Transcription Factors Negatively Regulate the Biosynthesis of Salicylic Acid and N-Hydroxypipecolic Acid by Modulating the Expression of SARD1 and CBP60g

Phosphorylation of the CAMTA3 Transcription Factor Triggers Its Destabilization and Nuclear Export

“…In conclusion, the recurrent isolation of CAMTA3 mutants in numerous independent genetic screens for pathogen/stress responses coupled with its posttranslational control through (direct/indirect) phosphorylation by possibly two stress-responsive kinase pathways positions it as a key node in (a)biotic stress signaling. Recent discovery of its negative regulation of genes involved in SA and N-hydroxypipecolic acid biosynthesis galvanizes its function in regulating immunity genes in SAR (Kim et al, 2020;Sun et al, 2020). Many gaps remain in the understanding of CAMTA3 regulation, but phosphorylation by multiple kinases, protein stability, and nucleo-cytoplasmic trafficking may be involved.…”

“…S8). All published EMSA results employed truncated CAMTA3 comprising only the DNA-binding domain (Du et al, 2009;Nie et al, 2012;Sun et al, 2020) while we used full-length CAMTA3, suggesting the presence of domains that regulate DNA binding. Future analysis of DNA binding may consider employing CAMTA3 fragments harboring most of the phospho-sites but lacking these negatively-acting domains.…”

Inducible biosynthesis and immune function of the systemic acquired resistance inducer N-hydroxypipecolic acid in monocotyledonous and dicotyledonous plants

“…Thus, in the absence of biotic challenge, plants apparently keep NHP at very low basal levels. Two recent studies have reported that Arabidopsis lines or mutant plants with constitutively elevated levels of NHP show permanently activated defenses and dwarfed phenotypes: specifically, lines overexpressing the calcium-dependent protein kinase CPK5 and mutants in which CAMTA3 , a negative immune-regulatory gene, is defective ( Guerra et al , 2020 ; Sun et al , 2020 ). When crossed with the fmo1 mutant, both lines lose their dwarfism and their ability to synthesize NHP, indicating that the growth retardation is caused by constitutively elevated levels of NHP.…”

“…The accumulation of Pip in leaf tissue of inoculated Arabidopsis is closely linked to a concomitant increase in the expression of the biosynthetic genes ALD1 and SARD4 , and the direct Pip precursor dehydropipecolic acid accumulates to detectable levels ( Návarová et al , 2012 ; Hartmann et al , 2017 ; Hartmann and Zeier, 2019 ). The immune-regulatory genes EDS1 and PAD4 , as well as several transcription factors, have been shown to regulate inducible ALD1 gene expression and the biosynthesis of Pip and NHP ( Návarová et al , 2012 ; Hartmann et al , 2018 ; Sun et al, 2018 , 2020 ; Wang et al , 2018 ; Kim et al , 2020 ). Similarly, the pathogen-induced accumulation of Pip in soybean is closely linked to a concomitant transcriptional induction of the soybean ALD1 homolog GmALD1 ( Abeysekara et al , 2016 ).…”

N-hydroxypipecolic acid: a general and conserved activator of systemic plant immunity

“…Intensive genetic analyses have uncovered several upstream components required for NHP biosynthesis in local and distal leaves (e.g. for the expression and translation of biosynthesis genes ALD1 or FMO1 ) and SAR, including SARD1 / CBP60g and PAD4 / EDS1 ( Hartmann et al , 2018 ; Sun et al ., 2018 , 2020 ; Guerra et al , 2020 ). In contrast, the mechanism of NHP perception and the nature of an NHP receptor still remain to be elucidated, though one candidate, NPR1 ( NONEXPRESSOR OF PR GENES 1 ), has already been put forward for discussion ( Hartmann and Zeier, 2019 ).…”