MEKK2 inhibits activation of MAP kinases in Arabidopsis

Nitta, Yukino; Qiu, Yue; Yaghmaiean, Hoda; Zhang, Qian; Huang, Jin‐Shun; Adams, Keith L.; Zhang, Yuelin

doi:10.1111/tpj.14763

Cited by 17 publications

(15 citation statements)

References 35 publications

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“…3l ). This echoes the observations that the kinase activity of MEKK2 is not required for triggering cell death, and MEKK2 may act as a structural protein, rather than a functional kinase, in the activation of SUMM2 24 , 41 . Taken together, the data indicate that MEKK2 likely scaffolds and stabilizes the SUMM2 and LET1 protein complex to activate autoimmunity.…”

supporting

confidence: 77%

“…Although the exact mechanism is not clear, the abundance of MEKK2 transcripts and proteins is positively correlated with the autoimmunity observed in the mekk1 , mkk1/2 , and mpk4 mutants 25 , 26 . Interestingly, MEKK2 has no detectable kinase activity and overexpression of WT MEKK2 and its kinase catalytic site mutant triggered a similar level of autoimmunity 24 , 41 . Thus, MEKK2 may play a structural role, rather than function as a kinase, in regulating SUMM2 accumulation.…”

mentioning

confidence: 99%

“…Thus, MEKK2 may play a structural role, rather than function as a kinase, in regulating SUMM2 accumulation. A recent study shows that MEKK2 might inhibit MPK4 activation by upstream MKKs 41 . We found here that MEKK2 interacts with both LET1 and SUMM2, and stabilizes LET1 and SUMM2 in a kinase activity-independent manner.…”

mentioning

confidence: 99%

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The malectin-like receptor-like kinase LETUM1 modulates NLR protein SUMM2 activation via MEKK2 scaffolding

Huang

Kong

et al. 2020

Nat. Plants

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Plants have evolved both cell surface-resident receptor-like kinases (RLKs) and intracellular nucleotide-binding leucine-rich repeat (NLR) proteins as immune receptors to detect infections. It remains enigmatic how RLK- and NLR-mediated signaling is connected. Disruption of an immune-activated MEKK1-MKK1/2-MPK4 MAPK cascade activates the NLR SUMM2 via the MAPK kinase kinase MEKK2, leading to autoimmunity. To gain insights into the mechanisms underlying SUMM2 activation, we deployed an RNAi-based genetic screen for mekk1 autoimmune suppressors, and identified an uncharacterized malectin-like RLK, named LETUM1 (LET1), as a specific regulator of mekk1-mkk1/2 - mpk4 autoimmunity via complexing with both SUMM2 and MEKK2. MEKK2 scaffolds LET1 and SUMM2 for protein stability and association, and counter-regulates the F-box protein CPR1-mediated SUMM2 ubiquitination and degradation; thereby, regulating SUMM2 accumulation and activation. Our study indicates that malectin-like RLK LET1 senses the perturbance of cellular homeostasis caused by the deficiency in immune-activated signaling, and activates the NLR SUMM2-mediated autoimmunity via MEKK2 scaffolding.

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supporting

confidence: 77%

mentioning

confidence: 99%

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The malectin-like receptor-like kinase LETUM1 modulates NLR protein SUMM2 activation via MEKK2 scaffolding

Huang

Kong

et al. 2020

Nat. Plants

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“…MAPKKK DELTA-1 (MKD1), an Arabidopsis (Arabidopsis thaliana) MAPKKK, is an exception as it cannot phosphorylate the classical serine or threonine residues in the activation loop but instead phosphorylates these residues in other functional domains of Arabidopsis MAPKK1 and MAPKK5 (Dietz et al, 2020). Similarly, Arabidopsis ENHANCED DISEASE RESISTANCE 1 (EDR1), CONSTITUTIVE TRIPLE RESPONSE 1 (CTR1) and MEKK2 do not phosphorylate the conserved S/T-X 5 -S/T motif in the MAPKK activation loop but negatively regulate MAPK cascade-mediated signal transduction via different mechanisms (Yoo et al, 2008;Zhao et al, 2014;Nitta et al, 2020;Gao et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

The rice Raf‐like MAPKKK OsILA1 confers broad‐spectrum resistance to bacterial blight by suppressing the OsMAPKK4–OsMAPK6 cascade

Chen

Wang

Yang

et al. 2021

JIPB

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Mitogen-activated protein kinase kinase kinase (MAPKKK) are the first components of MAPK cascades, which play pivotal roles in signaling during plant development and physiological processes. The genome of rice encodes 75 MAPKKKs, of which 43 are Raf-like MAPKKKs. The functions and action modes of most of the Raf-like MAPKKKs, whether they function as bona fide MAPKKKs and which are their downstream MAPKKs, are largely unknown. Here, we identified the osmapkkk43 mutant, which conferred broadspectrum resistance to Xanthomonas oryzae pv. oryzae (Xoo), the destructive bacterial pathogen of rice. Oryza sativa (Os)MAPKKK43 encoding a Raflike MAPKKK was previously known as Increased Leaf Angle 1 (OsILA1). Genetic analysis indicated that OsILA1 functioned as a negative regulator and acted upstream of the OsMAPKK4-OsMAPK6 cascade in rice-Xoo interactions. Unlike classical MAPKKKs, OsILA1 mainly phosphorylated the threonine 34 site at the N-terminal domain of Os-MAPKK4, which possibly influenced the stability of OsMAPKK4. The N-terminal domain of OsILA1 is required for its homodimer formation and its full phosphorylation capacity. Taken together, our findings reveal that OsILA1 acts as a negative regulator of the OsMAPKK4-OsMAPK6 cascade and is involved in rice-Xoo interactions.

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“…In contrast, several plant Raf family MAPKKKs can interact with downstream MAPKKs to promote MAPKKs degradation or suppress phosphorylation activity of MAPKKs on its direct downstream substrate MAPKs, but not directly phosphorylate and activate MAPKKs. Thus, some references suggest to exclude these plant Raf family MAPKKKs from bona fide MAPKKKs [54][55][56][57][58]. Compared with OsMAPKKs and OsMAPKs, rice has a great number of OsMAPKKKs, and more than half are Raf family MAPKKKs, the non-canonical MAPKKKs.…”

Section: Os01g47530 Os05g49140mentioning

confidence: 99%

Update on the Roles of Rice MAPK Cascades

Chen

Wang

Yuan

2021

IJMS

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The mitogen-activated protein kinase (MAPK) cascades have been validated playing critical roles in diverse aspects of plant biology, from growth and developmental regulation, biotic and abiotic stress responses, to phytohormone signal transduction or responses. A classical MAPK cascade consists of a MAPK kinase kinase (MAPKKK), a MAPK kinase (MAPKK), and a MAPK. From the 75 MAPKKKs, eight MAPKKs, and 15 MAPKs of rice, a number of them have been functionally deciphered. Here, we update recent advances in knowledge of the roles of rice MAPK cascades, including their components and complicated action modes, their diversified functions controlling rice growth and developmental responses, coordinating resistance to biotic and abiotic stress, and conducting phytohormone signal transduction. Moreover, we summarize several complete MAPK cascades that harbor OsMAPKKK-OsMAPKK-OsMAPK, their interaction with different upstream components and their phosphorylation of diverse downstream substrates to fulfill their multiple roles. Furthermore, we state a comparison of networks of rice MAPK cascades from signal transduction crosstalk to the precise selection of downstream substrates. Additionally, we discuss putative concerns for elucidating the underlying molecular mechanisms and molecular functions of rice MAPK cascades in the future.

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MEKK2 inhibits activation of MAP kinases in Arabidopsis

Cited by 17 publications

References 35 publications

The malectin-like receptor-like kinase LETUM1 modulates NLR protein SUMM2 activation via MEKK2 scaffolding

The malectin-like receptor-like kinase LETUM1 modulates NLR protein SUMM2 activation via MEKK2 scaffolding

The rice Raf‐like MAPKKK OsILA1 confers broad‐spectrum resistance to bacterial blight by suppressing the OsMAPKK4–OsMAPK6 cascade

Update on the Roles of Rice MAPK Cascades

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