Plant Cell最新文献

The phytohormone cytokinin (CK) positively regulates the activity of the inflorescence meristem (IM). Cytokinin oxidase 2/Grain number 1a (OsCKX2/Gn1a)-mediated degradation of CK in rice (Oryza sativa L.) negatively regulates panicle grain number, whereas DENSE AND ERECT PANICLE 1 (DEP1) positively regulates grain number per panicle (GNP). However, the detailed regulatory mechanism between DEP1 and OsCKX2 remains elusive. Here, we report the GRAS (GIBBERELLIN ACID INSENSITIVE, REPRESSOR OF GA1, and SCARECROW) transcription factor GRAIN NUMBER ASSOCIATED (GNA), previously thought to be involved in the Brassinosteroids (BRs) signaling pathway, directly inhibits OsCKX2 expression in the IM through a DEP1-GNA regulatory module. Overexpressing GNA leads to increased CK levels and consequently higher branch number, GNP, and yield. Both DEP1 and dep1 enhance the inhibitory effect of GNA on OsCKX2 expression through interacting with GNA. GNA promotes the translocation of DEP1 to the nucleus, while the gain-of-function mutant dep1 translocates into the nucleus in the absence of GNA. Our findings provide insight into the regulatory mechanism underlying OsCKX2 and a strategy to improve rice yield.

Well-conserved mitogen-activated protein kinase (MAPK) cascades are essential for orchestrating of a wide range of cellular processes in plants, including defense responses against pathogen attack. NAC transcription factors (TFs) play important roles in plant immunity, but their targets and how they are regulated remain largely unknown. Here, we identified the TF OsNAC29 as a key component of a MAPK signaling pathway involved in rice (Oryza sativa) disease resistance. OsNAC29 binds directly to CACGTG motifs in the promoters of OsTPS28 and OsCYP71Z2, which are crucial for the biosynthesis of the phytoalexin 5,10-diketo-casbene and consequently rice blast resistance. OsNAC29 positively regulates rice blast resistance by promoting the expression of of OsTPS28 and OsCYP71Z2, and the function of OsNAC29 is genetically dependent on OsCYP71Z2 and OsTPS28. Furthermore, OsNAC29 interacts with OsRACK1A and OsMAPK3/6 to form an immune complex; OsMAPK3 phosphorylates OsNAC29 at Thr304 to prevent its proteasome-mediated degradation and promote its function against rice blast fungus. Phosphorylation of OsNAC29 at Thr304 is induced upon Magnaporthe oryzae infection and chitin treatment. Our data demonstrate the positive role of the OsMAPK3-OsNAC29-OsTPS28/OsCYP71Z2 module in rice blast resistance, providing insights into the molecular regulatory network and fine-tuning of NAC TFs in rice immunity.

Salicylic acid (SA) is a prominent defense hormone whose basal level, organ-specific accumulation, and physiological role vary widely among plant species. Of the 2 known pathways of plant SA biosynthesis, the phenylalanine ammonia lyase (PAL) pathway is more ancient and universal but its biosynthetic and physiological roles in diverse plant species remain unclear. Studies in which the PAL pathway is specifically or completely inhibited, as well as a direct comparison of diverse species and different organs within the same species, are needed. To this end, we analyzed the PAL pathway in rice (Oryza sativa) and Arabidopsis (Arabidopsis thaliana), 2 distantly related model plants whose basal SA levels and distributions differ tremendously at the organism and tissue levels. Based on our recent identification of the rice peroxisomal cinnamate:CoA ligases (CNLs), we identified 2 peroxisomal CNLs from Arabidopsis and showed CNL as the most functionally specific enzyme among the known enzymes of the PAL pathway. We then revealed the species- and organ-specific contribution of the PAL pathway to benzoic and salicylic acid biosynthesis and clarified its physiological importance in rice and Arabidopsis. Our findings highlight the necessity to consider species and organ types in future SA-related studies and may help to breed new disease-resistant crops.

EARLY NODULIN 93 (ENOD93) has been genetically associated with biological nitrogen fixation in legumes and nitrogen use efficiency in cereals, but its precise function is unknown. We show that hidden Markov models define ENOD93 as a homolog of the N-terminal domain of RESPIRATORY SUPERCOMPLEX FACTOR 2 (RCF2). RCF2 regulates cytochrome oxidase (CIV), influencing the generation of a mitochondrial proton motive force in yeast (Saccharomyces cerevisiae). Knockout of ENOD93 in Arabidopsis (Arabidopsis thaliana) causes a short root phenotype and early flowering. ENOD93 is associated with a protein complex the size of CIV in mitochondria, but neither CIV abundance nor its activity changed in ruptured organelles of enod93. However, a progressive loss of ADP-dependent respiration rate was observed in intact enod93 mitochondria, which could be recovered in complemented lines. Mitochondrial membrane potential was higher in enod93 in a CIV-dependent manner, but ATP synthesis and ADP depletion rates progressively decreased. The respiration rate of whole enod93 seedlings was elevated, and root ADP content was nearly double that in wild type without a change in ATP content. We propose that ENOD93 and HYPOXIA-INDUCED GENE DOMAIN 2 (HIGD2) are the functional equivalent of yeast RCF2 but have remained undiscovered in many eukaryotic lineages because they are encoded by 2 distinct genes.

Multiple plant hormones, including strigolactone (SL), play key roles in regulating flowering time. The Arabidopsis (Arabidopsis thaliana) DWARF14 (AtD14) receptor perceives SL and recruits F-box protein MORE AXILLARY GROWTH2 (MAX2) and the SUPPRESSOR OF MAX2-LIKE (SMXL) family proteins. These interactions lead to the degradation of the SMXL repressor proteins, thereby regulating shoot branching, leaf shape, and other developmental processes. However, the molecular mechanism by which SL regulates plant flowering remains elusive. Here, we demonstrate that intact strigolactone biosynthesis and signaling pathways are essential for normal flowering in Arabidopsis. Loss-of-function mutants in both SL biosynthesis (max3) and signaling (Atd14 and max2) pathways display earlier flowering, whereas the repressor triple mutant smxl6/7/8 (s678) exhibits the opposite phenotype. Retention of AtD14 in the cytoplasm leads to its inability to repress flowering. Moreover, we show that nuclear-localized AtD14 employs dual strategies to enhance the function of the AP2 transcription factor TARGET OF EAT1 (TOE1). AtD14 directly binds to TOE1 in an SL-dependent manner and stabilizes it. In addition, AtD14-mediated degradation of SMXL7 releases TOE1 from the repressor protein, allowing it to bind to and inhibit the FLOWERING LOCUS T (FT) promoter. This results in reduced FT transcription and delayed flowering. In summary, AtD14 perception of SL enables the transcription factor TOE1 to repress flowering, providing insights into hormonal control of plant flowering.

Autoluminescent plants have been genetically modified to express the fungal bioluminescence pathway (FBP). However, a bottleneck in precursor production has limited the brightness of these luminescent plants. Here, we demonstrate the effectiveness of utilizing a computational model to guide a multiplex five-gene-silencing strategy by an artificial microRNA array to enhance caffeic acid (CA) and hispidin levels in plants. By combining loss-of-function-directed metabolic flux with a tyrosine-derived CA pathway, we achieved substantially enhanced bioluminescence levels. We successfully generated eFBP2 plants that emit considerably brighter bioluminescence for naked-eye reading by integrating all validated DNA modules. Our analysis revealed that the luminous energy conversion efficiency of the eFBP2 plants is currently very low, suggesting that luminescence intensity can be improved in future iterations. These findings highlight the potential to enhance plant luminescence through the integration of biological and information technologies.