Publications
Aryal, B.; Xia, J.; Hu, Z.; Stumpe, M.; Tsering, T.; Liu, J.; Huynh, J.; Fukao, Y.; Glöckner, N.; Huang, H.-Y.; Sancho-Andrés, G.; Pakula, K.; Ziegler, J.; Gorzolka, K.; Zwiewka, M.; Nodzynski, T.; Harter, K.; Sánchez-Rodríguez, C.; Jasiński, M.; Rosahl, S.; Geisler, M. M.; An LRR receptor kinase controls ABC transporter substrate preferences during plant growth-defense decisions Curr. Biol. 33, 2008-2023, (2023) DOI: 10.1016/j.cub.2023.04.029
The exporter of the auxin precursor indole-3-butyric acid (IBA), ABCG36/PDR8/PEN3, from the model plant Arabidopsis has recently been proposed to also function in the transport of the phytoalexin camalexin. Based on these bonafide substrates, it has been suggested that ABCG36 functions at the interface between growth and defense. Here, we provide evidence that ABCG36 catalyzes the direct, ATP-dependent export of camalexin across the plasma membrane. We identify the leucine-rich repeat receptor kinase, QIAN SHOU KINASE1 (QSK1), as a functional kinase that physically interacts with and phosphorylates ABCG36. Phosphorylation of ABCG36 by QSK1 unilaterally represses IBA export, allowing camalexin export by ABCG36 conferring pathogen resistance. As a consequence, phospho-dead mutants of ABCG36, as well as qsk1 and abcg36 alleles, are hypersensitive to infection with the root pathogen Fusarium oxysporum, caused by elevated fungal progression. Our findings indicate a direct regulatory circuit between a receptor kinase and an ABC transporter that functions to control transporter substrate preference during plant growth and defense balance decisions.
Publications
Abukhalaf, M.; Proksch, C.; Thieme, D.; Ziegler, J.; Hoehenwarter, W.; Changing turn-over rates regulate abundance of tryptophan, GS biosynthesis, IAA transport and photosynthesis proteins in Arabidopsis growth defense transitions BMC Biol. 21, 249, (2023) DOI: 10.1186/s12915-023-01739-3
Background
Shifts in dynamic equilibria of the abundance of cellular molecules in plant-pathogen interactions need further exploration. We induced PTI in optimally growing Arabidopsis thaliana seedlings for 16 h, returning them to growth conditions for another 16 h.
Methods
Turn-over and abundance of 99 flg22 responding proteins were measured chronologically using a stable heavy nitrogen isotope partial labeling strategy and targeted liquid chromatography coupled to mass spectrometry (PRM LC–MS). These experiments were complemented by measurements of mRNA and phytohormone levels.
Results
Changes in synthesis and degradation rate constants (Ks and Kd) regulated tryptophane and glucosinolate, IAA transport, and photosynthesis-associated protein (PAP) homeostasis in growth/PTI transitions independently of mRNA levels. Ks values increased after elicitation while protein and mRNA levels became uncorrelated. mRNA returned to pre-elicitation levels, yet protein abundance remained at PTI levels even 16 h after media exchange, indicating protein levels were robust and unresponsive to transition back to growth. The abundance of 23 PAPs including FERREDOXIN-NADP( +)-OXIDOREDUCTASE (FNR1) decreased 16 h after PAMP exposure, their depletion was nearly abolished in the myc234 mutant. FNR1 Kd increased as mRNA levels decreased early in PTI, its Ks decreased in prolonged PTI. FNR1 Kd was lower in myc234, mRNA levels decreased as in wild type.
Conclusions
Protein Kd and Ks values change in response to flg22 exposure and constitute an additional layer of protein abundance regulation in growth defense transitions next to changes in mRNA levels. Our results suggest photosystem remodeling in PTI to direct electron flow away from the photosynthetic carbon reaction towards ROS production as an active defense mechanism controlled post-transcriptionally and by MYC2 and homologs. Target proteins accumulated later and PAP and auxin/IAA depletion was repressed in myc234 indicating a positive effect of the transcription factors in the establishment of PTI.
Publications
Bassal, M.; Abukhalaf, M.; Majovsky, P.; Thieme, D.; Herr, T.; Ayash, M.; Tabassum, N.; Al Shweiki, M. R.; Proksch, C.; Hmedat, A.; Ziegler, J.; Lee, J.; Neumann, S.; Hoehenwarter, W.; Reshaping of the Arabidopsis thaliana Proteome Landscape and Co-regulation of Proteins in Development and Immunity Mol. Plant 13, 1709-1732, (2020) DOI: 10.1016/j.molp.2020.09.024
Proteome remodeling is a fundamental adaptive response, and proteins in
complexes and functionally related proteins are often co-expressed.
Using a deep sampling strategy we define core proteomes of Arabidopsis thaliana
tissues with around 10 000 proteins per tissue, and absolutely quantify
(copy numbers per cell) nearly 16 000 proteins throughout the plant
lifecycle. A proteome-wide survey of global post-translational
modification revealed amino acid exchanges pointing to potential
conservation of translational infidelity in eukaryotes. Correlation
analysis of protein abundance uncovered potentially new tissue- and
age-specific roles of entire signaling modules regulating transcription
in photosynthesis, seed development, and senescence and abscission.
Among others, the data suggest a potential function of RD26 and other
NAC transcription factors in seed development related to desiccation
tolerance as well as a possible function of cysteine-rich receptor-like
kinases (CRKs) as ROS sensors in senescence. All of the components of
ribosome biogenesis factor (RBF) complexes were found to be co-expressed
in a tissue- and age-specific manner, indicating functional promiscuity
in the assembly of these less-studied protein complexes in Arabidopsis. Furthermore, we characterized detailed proteome remodeling in basal immunity by treating Arabidopsis
seeldings with flg22. Through simultaneously monitoring
phytohormone and transcript changes upon flg22 treatment, we obtained
strong evidence of suppression of jasmonate (JA) and JA-isoleucine
(JA-Ile) levels by deconjugation and hydroxylation by IAA-ALA RESISTANT3
(IAR3) and JASMONATE-INDUCED OXYGENASE 2 (JOX2), respectively, under
the control of JASMONATE INSENSITIVE 1 (MYC2), suggesting an
unrecognized role of a new JA regulatory switch in pattern-triggered
immunity. Taken together, the datasets generated in this study present
extensive coverage of the Arabidopsis proteome in various biological scenarios, providing a rich resource available to the whole plant science community.