The Plant Journal最新文献

Oomycete pathogens deliver a number of RxLR effector proteins into host plant cells to manipulate immunity by targeting diverse host proteins. Here, we reveal that a Phytophthora infestans RxLR effector Pi18609 targets a potato B-box transcription factor (BBX), StBBX27, which was identified to positively regulate late blight resistance. Silencing the ortholog NbBBX27 in Nicotiana benthamiana or RNA interfering StBBX27 in potato increases host colonization by P. infestans, whereas transient expression of StBBX27 in N. benthamiana or stable overexpression of StBBX27 in potato enhances late blight resistance. Overexpression of StBBX27 in potato activates plant immune responses including upregulation of defense-related genes such as StWRKY8, StOSML13, StCHTB4, and StSERK2, and burst of reactive oxygen species (ROS). In addition, StBBX27 directly binds to the G-box of the WRKY8 and SERK2 promoters and activates their expression, which could be suppressed by Pi18609. Furthermore, we revealed that a ubiquitin E3 ligase COP1 promotes StBBX27 turnover by a proteasome-mediated system. Moreover, Pi18609 promotes the degradation of StBBX27 mediated by COP1. Collectively, this study reveals that StBBX27 positively regulates potato immunity and that is suppressed by effector Pi18609 to promote its turnover. This research extends our knowledge on BBXs function and the mechanisms behind P. infestans effectors suppression of host immunity.

The regulatory mechanisms underlying fruit ripening, including hormone regulation, transcription factor activity, and epigenetic modifications, have been discussed extensively. Nonetheless, the role of long non-coding RNAs (lncRNAs) in fruit ripening remains unclear. Here, we identified lncRNA1471 as a negative regulator of tomato fruit-ripening initiation. Knocking out lncRNA1471 via large fragment deletion resulted in accelerated initiation of fruit ripening, a shorter color-breaking stage (BR), deeper coloration, increased levels of ethylene, lycopene, and β-carotene, accelerated chlorophyll degradation, and reduced fruit firmness. These phenotypic changes were accompanied by alterations in the carotenoid pathway flux, ethylene biosynthesis, and cell wall metabolism, primarily mediated by the direct regulation of key genes involved in these processes. For example, in the CR-lncRNA1471 mutant, lycopene-related SlPSY1 and SlZISO were upregulated. Additionally, the expression levels of ethylene biosynthetic genes (SlACS2 and SlACS4), ripening-related genes (RIN, NOR, CNR, and SlDML2), and cell wall metabolism genes (SlPL, SlPG2a, SlEXP1, SlPMEI-like, and SlBG4) were significantly upregulated, which further strengthening the findings mentioned above. Furthermore, lncRNA1471 was identified to interact with the abscisic stress-ripening protein (ASR) transcription factor by chromatin isolation by RNA purification coupled with mass spectrometry (ChIRP-MS) and protein pull-down assay in vitro, which might regulate key genes involved in tomato ripening. The discovery of the significant non-coding regulator lncRNA1471 enhances our understanding of the complex regulatory landscape governing fruit ripening. These findings provide valuable insights into the mechanisms underlying ripening, particularly regarding the involvement of lncRNAs in ripening.

Interaction of dimeric 14-3-3 proteins with phosphotargets regulates various physiological processes in plants, from flowering to transpiration and salt tolerance. Several genes express distinct 14-3-3 “isoforms,” particularly numerous in plants, but these are unevenly studied even in model species. Here we systematically investigated twelve 14-3-3 isoforms from Arabidopsis thaliana. While all these proteins can homodimerize, four isoforms representing a supposedly more ancestral, epsilon phylogenetic group (iota, mu, omicron, epsilon), but not their eight non-epsilon counterparts (omega, phi, chi, psi, upsilon, nu, kappa, lambda), exhibit concentration-dependent monomerization, and pronounced surface hydrophobicity at physiologically relevant protein concentrations and under crowding conditions typical for the cell. We show that dramatically lowered thermodynamic stabilities entail aggregation of the epsilon group isoforms at near-physiological temperatures and accelerate their proteolytic degradation in vitro and in plant cell lysates. Mutations in 14-3-3 iota, inspired by structural analysis, helped us rescue non-epsilon behavior and pinpoint key positions responsible for the epsilon/non-epsilon demarcation. Combining two major demarcating positions (namely, 27th and 51st in omega) and differences in biochemical properties, we developed an epsilon/non-epsilon demarcation criterion that classified 89% of available 14-3-3 sequences from Dicots, Monocots, Gymnosperms, Ferns, and Lycophytes with 99.7% accuracy, and reliably predicted biochemical properties of a given 14-3-3 isoform, which we experimentally verified for distant 14-3-3 isoforms from Selaginella moellendorffii. The proven occurrence of isoforms of both groups in primitive plants refines the traditional phylogenetic, solely sequence-based analysis and provides intriguing insights into the evolutionary history of the epsilon phylogenetic group.

In the climacteric fruit tomato (Solanum lycopersicum), 1-aminocyclopropane-1-carboxylic acid (ACC) synthase 2 (ACS2) and ACS4 are jointly recognized as key enzymes in orchestrating System-2 ethylene biosynthesis during fruit ripening. However, the precise roles and individual contributions of ACS2 and ACS4 within this process remain elusive. Here, we generate acs2, acs4 single knockout, and acs2/4 double knockout mutants through the CRISPR/Cas9 system. Our results reveal that the knockout of ACS2 leads to a modest decrease in ethylene production, with minimal effects on fruit ripening. In contrast, the knockout of ACS4 unveils a severe ripening defect akin to that observed in the acs2/4 mutant, which stems from a profound disruption of ethylene autocatalytic biosynthesis, ultimately resulting in inadequate ethylene production vital for supporting fruit ripening. Transcriptome analysis, in conjunction with exogenous ethylene treatment, conclusively demonstrates a pronounced dose-dependent correlation between fruit ripening and ethylene, wherein varying doses of ethylene distinctly regulate the expression of a substantial number of ripening-related genes, eventually controlling both the ripening process and quality formation. These findings clarify the pivotal role of ACS4 in ethylene biosynthesis compared to ACS2 and deepen our understanding of the fine-tuned regulation of ethylene in climacteric fruit ripening.

High temperature influence flower bud differentiation in Physalis grisea, resulting in the production of deformed fruits and affects fruit yield and quality. However, the molecular mechanisms underlying the response of P. grisea to heat stress (HS) remain unclear. In this study, HS treatment and dynamic transcriptome analysis of P. grisea identified the PgCDF2-PgHSFA1/PgHSFB3 transcriptional regulatory module as playing a key role in the response of P. grisea to HS. Gene Ontology (GO) enrichment analysis, transcriptional regulation prediction, and weighted correlation network analysis (WGCNA) of heat stress (HS)-responsive transcriptome data identified three key genes, PgCDF2, PgHSFA1 and PgHSFB3, as components of the regulatory network of heat stress in P. grisea. The expression levels of PgCDF2, PgHSFA1, and PgHSFB3 were up-regulated following exposure to HS. Silencing of PgHSFA1 and PgHSFB3 resulted in reduced heat stress tolerance and altered reactive oxygen species levels in P. grisea. Dual-luciferase assay and Electrophoretic Mobility Shift Assay (EMSA) results indicate that PgCDF2 binds to the promoters of PgHSFA1 and PgHSFB3 and activate their expression. Silencing of PgCDF2 inhibited the expression of PgHSFA1 and PgHSFB3 and also reduced the heat tolerance of P. grisea. In summary, under HS, PgCDF2 enhances the heat tolerance of P. grisea by activating the expression of PgHSFA1 and PgHSFB3. This study clarifies the role of the PgCDF2-PgHSFA1/PgHSFB3 module in the response of P. grisea to HS, providing a theoretical basis for a more in-depth analysis of the molecular mechanisms underlying this response.

As the staple food for more than half of the world's population, rice requires elite varieties with superior quality and high yield to ensure food security. Agronomic traits, such as grain size, leaf angle, seed dormancy, and germination, will affect rice yield. Identification and cloning of key genes and elucidation of molecular mechanisms regulating these traits expedite rice breeding. The OVATE Family Proteins (OFPs), a unique family of transcription regulators, play critical roles in regulating grain or fruit size, plant morphology, and stress responses. Here, we have successfully identified OsOFP9, an uncharacterized OFP member in rice, and demonstrated its irreplaceable role in controlling several key agronomic traits. Mutation of OsOFP9 results in severe pre-harvest sprouting, promoted seed germination, smaller grains, and reduced leaf angle. Mechanistic studies revealed that the OsOFP9 mutation reduced abscisic acid (ABA) levels and increased gibberellin (GA) levels, thereby affecting the ABA/GA ratio and α-amylase activity. In addition, OsOFP9 directly interacts with GS9 and DLT, key transcriptional regulators involved in the BR signaling pathway controlling grain size and leaf angle, respectively. Functional assays showed that OsOFP9 inhibited the transcriptional activation activity of GS9, but enhanced the transcriptional repression activity of DLT. Genetic evidence showed that GS9 and DLT function downstream of OsOFP9, consistent with the results of the transcriptional activity assay. In conclusion, this study reveals the crucial role of OsOFP9 in regulating several important agronomic traits and elucidates its molecular mechanism in coordinating multiple plant hormones, thus providing valuable insights and genetic resources for improving rice yield.