Biology subjects

Klecker, M.

Publications and source records attributed to Klecker, M..

3 recordsLinked to original sources

bioRxiv2023

PHR1 and PHL1 mediate rapid high-light responses and acclimation to triose phosphate oversupply

O_LIRapid acclimation towards high light is vital for the prevention of phototoxic stress to plant tissues. Photosynthesis transiently consumes inorganic phosphate (Pi). We therefore asked whether changes in intracellular Pi pools can act as a signal for reprogramming gene expression upon increased light intensity. C_LIO_LIThe function of triose phosphate utilization for intracellular Pi homeostasis was deciphered by investigation of mutants defective in both photoassimilate partitioning and low-Pi signaling. Next, we determined subcellular Pi levels and transcript accumulation upon short-term high light. Physiological consequences were examined by analyses of ATP, carbohydrates, and an untargeted lipid profiling approach. C_LIO_LIThe capacity for triose phosphate utilization clearly affected systemic Pi signaling. High-light treatment caused a rapid depletion specifically of chloroplast Pi levels paralleled by induction of transcripts dependent on PHOSPHATE STARVATION RESPONSE 1 (PHR1) and PHR1-LIKE 1. Among the high-light induced targets of PHR1, SRG3/GDPD1 is involved in phospholipid catabolism. Lipid profiling revealed differences between WT and srg3 mutant plants upon high light, including changes in linolenic acid and photoprotective zeaxanthin. C_LIO_LIWe conclude that photosynthetic activity regulates the low-Pi response machinery in the nucleus to implement high-light acclimation. This facilitates the liberation of cellular P as well as the maintenance of membrane lipid integrity. C_LI

plant biology↗

bioRxiv2019

Differential N-end rule degradation of RIN4/NOI fragments generated by the AvrRpt2 effector protease

The protein RPM1-INTERACTING PROTEIN4 (RIN4) is a central regulator of both layers of plant immunity systems, the so-called pattern-triggered immunity (PTI) and effector-triggered immunity (ETI). RIN4 is targeted by several effectors, including the Pseudomonas syringae protease effector AvrRpt2. Cleavage of RIN4 by AvrRpt2 generates unstable RIN4 fragments, whose degradation leads to the activation of the resistance protein RPS2 (RESISTANT TO P. SYRINGAE2). Hence, identifying the determinants of RIN4 degradation is key to understanding RPS2-mediated ETI, as well as virulence functions of AvrRpt2. In addition to RIN4, AvrRpt2 cleaves host proteins from the nitrate-induced (NOI) domain family. Although cleavage of NOI-domain proteins by AvrRpt2 may contribute to PTI regulation, the (in)stability of these proteolytic fragments and the determinants that regulate their stability have not been examined. Notably, a common feature of RIN4 and of many NOI-domain protein fragments generated by AvrRpt2 cleavage is the exposure of a new N-terminal residue that is destabilizing according to the N-end rule. Using antibodies raised against endogenous RIN4, we show that the destabilization of AvrRpt2-cleaved RIN4 fragments is independent of the N-end rule pathway (recently renamed N-degron pathway). By contrast, several NOI-domain protein fragments are bona fide substrates of the N-degron pathway. The discovery of this novel set of substrates considerably expands the number of proteins targeted for degradation by this ubiquitin-dependent pathway, for which very few physiological substrates are known in plants. Our results also open new avenues of research to understand the role of AvrRpt2 in promoting bacterial virulence.\n\nOne sentence summaryAnalysis of RIN4/NOI fragments released after cleavage by the bacterial effector protease AvrRpt2 reveals a novel role of the N-end rule in the degradation of NOI-domain proteins, but not of RIN4.

plant biology↗

bioRxiv2016

Ubiquitylation activates a peptidase that promotes cleavage and destabilization of its activating E3 ligases and diverse growth regulatory proteins to limit cell proliferation in Arabidopsis

The characteristic shapes and sizes of organs are established by cell proliferation patterns and final cell sizes, but the underlying molecular mechanisms coordinating these are poorly understood. Here we characterize a ubiquitin-activated peptidase called DA1 that limits the duration of cell proliferation during organ growth in Arabidopsis thaliana. The peptidase is activated by two RING E3 ligases, BB and DA2, which are subsequently cleaved by the activated peptidase and destabilized. In the case of BB, cleavage leads to destabilization by the RING E3 ligase PRT1 of the N-end rule pathway. DA1 peptidase activity also cleaves the de-ubiquitylase UBP15, which promotes cell proliferation, and the transcription factors TCP15 and TCP22, which promote cell proliferation proliferation and repress endoreduplication. We propose that DA1 peptidase activity regulates the duration of cell proliferation and the transition to endoreduplication and differentiation during organ formation in plants by coordinating the destabilization of regulatory proteins.

plant biology↗