Molecular Plant最新文献

Hornworts are the only land plants that employ a pyrenoid to optimize Rubisco's CO₂ fixation. Yet, hornwort Rubisco remains poorly characterized. Here we assemble 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 μM) and specificity (∼70) for CO₂. In other words, hornwort Rubiscos do not comply with the long held canonical 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 interactions, when RbcX is absent during biogenesis, increases the accessibility of active sites and catalytic turnover rate. This study uncovered a previously unknown Rubisco kinetic parameter space and provides a SynBio chassis to expand the survey of other Rubisco kinetics. Our discovery could thus reshape the approaches for engineering Rubisco with superior kinetics.

Pattern recognition receptors (PRRs) are integral to plant immunity, functioning as the first line of defense against pathogens. Among these, receptor kinases (RKs) play a critical role in recognizing external signals and initiating immune responses. Recent studies by Li et al. (2024) have identified the G-type lectin receptor kinase ZmLecRK1 in maize as essential for resistance to Pythium aphanidermatum and other fungal pathogens. A key finding is that a resistant variant of ZmLecRK1, which carries an alanine at position 404, has emerged in maize, while the ancestral form, with a serine at this position, is conserved across most grasses. This amino acid substitution significantly influences the interaction with the co-receptor BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED RECEPTOR KINASE 1 (BAK1), enhancing immune complex formation and subsequent defense signaling. This work underscores the importance of genetic variation in enhancing disease resistance, offering potential strategies for crop improvement through targeted genetic modification.

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 demonstrate that the receptor-like kinase MALE DISCOVERER 1-INTERACTING RECEPTOR-LIKE KINASE 2 (MIK2) functions as a negative regulator of leaf senescence. We report that the SERINE-RICH ENDOGENOUS PEPTIDE 12, previously known to physically interact with MIK2, competes with SCOOP10 to control MIK2-dependent senescence regulatory mechanisms. We observed that increased expression of SCOOP10 or the application of exogenous SCOOP10 peptides accelerated leaf senescence in a MIK2-dependent manner. Conversely, SCOOP12 acted as a suppressor of MIK2-dependent senescence regulation. We also found that SCOOP12 enhanced while SCOOP10 diminished MIK2 phosphorylation. Thus, the SCOOP12-MIK2 module might function antagonistically on SCOOP10-MIK2 signaling at late senescing stages, allowing for fine-tuned modulation of the leaf senescence process. Our research 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.

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 at the 5' cap of WUS mRNA to protect it from degradation. We demonstrated that protein-folding genes are repressed by WUS to maintain precise protein synthesis in stem cells by preventing the reuse of misfolded proteins. However, upon heat stress, the MYB3R-like/RID2 module is repressed to reduce WUS transcripts via the decapping of nascent WUS mRNA. This releases the inhibition of protein folding capacity in stem cells and protects plant stem cells from heat-shock by eliminating misfolded protein aggregation. Our results reveal a tradeoff strategy in plants by reducing the accuracy of protein synthesis in exchange for the survival of stem cells at high temperatures.

Root-knot nematodes (RKNs) are plant pests that infect the roots of host plants. Bacillus thuringiensis (Bt) nematicidal proteins exhibited toxicity to nematodes. However, the application of nematicidal proteins for plant protection is hampered by the lack of effective delivery systems in transgenic plants. In this study, we discovered the accumulation of leucoplasts (root plastids) in galls and RKN-induced giant cells. RKN infection causes the degradation of leucoplasts into small vesicle-like structures, which are responsible for delivering proteins to RKNs, as observed through confocal microscopy and immunoelectron microscopy. We showed that different-sized proteins from leucoplasts could be taken up by Meloidogyne incognita female. To further explore the potential applications of leucoplasts, we introduced the Bt crystal protein Cry5Ba2 into tobacco and tomato leucoplasts by fusing it with a transit peptide. The transgenic plants showed significant resistance to RKNs. Intriguingly, RKN females preferentially took up Cry5Ba2 protein when delivered through plastids rather than the cytosol. The decrease in progeny was positively correlated with the delivery efficiency of the nematicidal protein. In conclusion, this study offers new insights into the feeding behavior of RKNs and their ability to ingest leucoplast proteins, and demonstrates that root leucoplasts can be used for delivering nematicidal proteins, thereby offering a promising approach for nematode control.

Cold stress is one of the major abiotic stress factors affecting rice growth and development, leading to significant yield loss in the context of global climate change. Exploring natural variants that confer cold resistance and the underlying molecular mechanism responsible for this is the major strategy to breed cold-tolerant rice varieties. Here, we show that natural variations of a SIMILAR to RCD ONE (SRO) gene, OsSRO1c, confer cold tolerance in rice at both seedling and booting stages. Our in vivo and in vitro experiments demonstrated that OsSRO1c possesses intrinsic liquid-liquid phase-separation ability and recruits OsDREB2B, an AP2/ERF transcription factor that functions as a positive regulator of cold stress, into its biomolecular condensates in the nucleus, resulting in elevated transcriptional activity of OsDREB2B. We found that the OsSRO1c-OsDREB2B complex directly responds to low temperature through dynamic phase transitions and regulates key cold-response genes, including COLD1. Furthermore, we showed that introgression of an elite haplotype of OsSRO1c into a cold-susceptible indica rice could significantly increase its cold resistance. Collectively, our work reveals a novel cold-tolerance regulatory module in rice and provides promising genetic targets for molecular breeding of cold-tolerant rice varieties.