查看更多>>摘要：Leaf senescence plays a critical role in a plant's overall reproductive success due to its involvement in nutrient remobilization and allocation.However,our current understanding of the molecular mechanisms controlling leaf senescence remains limited.In this study,we show that the receptor-like kinase MALE DISCOVERER 1-INTERACTING RECEPTOR-LIKE KINASE 2(MIK2)functions as a negative regulator of leaf senescence.We found that the SERINE-RICH ENDOGENOUS PEPTIDE 12,previously known to phys-ically interact with MIK2,competes with SCOOP10 to regulate MIK2-dependent leaf senescence.We observed that increased expression of SCOOP10 or the application of exogenous SCOOP10 peptides accelerated leaf senescence in a MIK2-depen dent manner.Conversely,SCOOP12 acted as a suppressor of MIK2-dependent leaf senescence regulation.Biochemical assays showed that SCOOP12 enhances while SCOOP10 diminishes MIK2 phosphorylation.Thus,the SCOOP12-MIK2 module might function antag-onistically on SCOOP10-MIK2 signaling at late senescing stages,allowing for fine-tuned modulation of the leaf senescence process.Our study sheds light on the complex mechanisms underlying leaf senescence and provides valuable insights into the interplay between receptors,peptides,and the regulation of plant senescence.
查看更多>>摘要：The plasticity of stem cells in response to environmental change is critical for multicellular organisms.Here,we show that MYB3R-like directly activates the key plant stem-cell regulator WUSCHEL(WUS)by recruiting the methyltransferase ROOT INITIATION DEFECTIVE 2(RID2),which functions in m7G methylation of the 5'cap of WUS mRNA to protect it from degradation.Transcriptomic and molecular analyses showed that protein-folding genes are repressed by WUS to maintain precise protein synthesis in stem cells by prevent-ing the reuse of misfolded proteins.Interestingly,we found that upon heat stress,the MYB3R-like/RID2 module is repressed to reduce WUS transcript abundance through decapping of nascent WUS mRNA.This releases the inhibition of protein-folding capacity in stem cells and protects them from heat shock by eliminating misfolded protein aggregation.Taken together,our results reveal a strategic trade-off whereby plants reduce the accuracy of protein synthesis in exchange for the survival of stem cells at high temperatures.
Zhen Guo OhTanner Ashton RobisonDan Hong LohWarren Shou Leong Ang...
1833-1849页
查看更多>>摘要：Hornworts are the only land plants that employ a pyrenoid to optimize Rubisco's CO2 fixation,yet hornwort Rubisco remains poorly characterized.Here we assembled the hornwort Anthoceros agrestis Rubisco(AaRubisco)using the Arabidopsis thaliana SynBio expression system and observed the formation of stalled intermediates,prompting us to develop a new SynBio system with A.agrestis cognate chaperones.We successfully assembled AaRubisco and Rubisco from three other hornwort species.Unlike A.thaliana Rubisco,AaRubisco assembly is not dependent on RbcX or Raf2.Kinetic characterization reveals that hornwort Rubiscos exhibit a range of catalytic rates(3-10 s-1),but with similar affinity(～30 μ.M)and spec-ificity(～70)for CO2.These results suggest that hornwort Rubiscos do not comply with the long-held canon-ical catalytic trade-off observed in other land plants,providing experimental support that Rubisco kinetics may be phylogenetically constrained.Unexpectedly,we observed a 50％increase in AaRubisco catalytic rates when RbcX was removed from our SynBio system,without any reduction in specificity.Structural biology,biochemistry,and proteomic analysis suggest that subtle differences in Rubisco large-subunit in-teractions,when RbcX is absent during biogenesis,increases the accessibility of active sites and catalytic turnover rate.Collectively,this study uncovered a previously unknown Rubisco kinetic parameter space and provides a SynBio chassis to expand the survey of other Rubisco kinetics.Our discoveries will contribute to developing new approaches for engineering Rubisco with superior kinetics.
查看更多>>摘要：Hormone perception and signaling pathways have a fundamental regulatory function in the physiological processes of plants.Cytokinins,a class of plant hormones,regulate cell division and meristem maintenance.The cytokinin signaling pathway is well established in the model plant Arabidopsis thaliana.Several negative feedback mechanisms,tightly controlling cytokinin signaling output,have been described previously.In this study,we identified a new feedback mechanism executed through alternative splicing of the cytokinin recep-tor AHK4/CRE1.A novel splicing variant named CRE1int7 results from seventh intron retention,introducing a premature termination codon in the transcript.We showed that CRE1int7 is translated in planta into a truncated receptor lacking the C-terminal receiver domain essential for signal transduction.CRE1int7 can bind cytokinin but cannot activate the downstream cascade.We present a novel negative feedback mecha-nism of the cytokinin signaling pathway,facilitated by a decoy receptor that can inactivate canonical cyto-kinin receptors via dimerization and compete with them for ligand binding.Ensuring proper plant growth and development requires precise control of the cytokinin signaling pathway at several levels.CRE1int7 rep-resents a so-far unknown mechanism for fine-tuning the cytokinin signaling pathway in Arabidopsis.
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