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Aromatic Cytokinin Arabinosides Promote PAMP-like Responses and Positively Regulate Leaf Longevity
journal contribution
posted on 2020-06-29, 12:39 authored by Magdaléna Bryksová, Siarhei Dabravolski, Zuzana Kučerová, Filip Zavadil Kokáš, Martina Špundová, Lucie Plíhalová, Tomáš Takáč, Jiří Grúz, Martin Hudeček, Veronika Hloušková, Radoslav Koprna, Ondřej Novák, Miroslav Strnad, Ondřej Plíhal, Karel DoležalCytokinins
are plant hormones with biological functions ranging
from coordination of plant growth to the regulation of biotic and
abiotic stress-related responses and senescence. The components of
the plant immune system can learn from past elicitations by microbial
pathogens and herbivores and adapt to new threats. It is known that
plants can enter the primed state of enhanced defense induced by either
natural or synthetic compounds. While the involvement of cytokinins
in defense priming has been documented, no comprehensive model of
their action has been provided to date. Here, we report the functional
characterization of two aromatic cytokinin derivatives, 6-benzylaminopurine-9-arabinosides
(BAPAs), 3-methoxy-BAPA and 3-hydroxy-BAPA, that proved to be effective
in delaying senescence in detached leaves while having low interactions
with the cytokinin pathway. An RNA-seq profiling study on Arabidopsis leaves treated with 3-methoxy-BAPA revealed
that short and extended treatments with this compound shifted the
transcriptional response markedly toward defense. Both treatments
revealed upregulation of genes involved in processes associated with
plant innate immunity such as cell wall remodeling and upregulation
of specific MAP kinases, most importantly MPK11,
which is a MAPK module involved in stress-related signaling during
the pathogen-associated molecular patterns (PAMPs) response. In addition,
elevated levels of JA and its metabolites, jasmonate/ethylene-driven
upregulation of PLANT DEFENSIN 1.2 (PDF1.2) and other defensins, and also temporarily elevated levels of reactive
oxygen species marked the plant response to 3-methoxy-BAPA treatment.
Synergistic interactions were observed when plants were cotreated
with 3-hydroxy-BAPA and the flagellin-derived bacterial PAMP peptide
(flg22), leading to the enhanced expression of the PAMP-triggered
immunity (PTI) marker gene FRK1. Our data collectively
show that some BAPAs can sensitively prime the PTI responses in a
low micromolar range of concentrations while having no observable
negative effects on the overall fitness of the plant.