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BACKGROUND: Plant immunity relies on the perception of immunogenic signals by cell-surface and intracellular receptors and subsequent activation of defense responses like programmed cell death. Under certain circumstances, the fine-tuned innate immune system of plants results in the activation of autoimmune responses that cause constitutive defense responses and spontaneous cell death in the absence of pathogens.; RESULTS: Here, we characterized the onset of leaf death 12 (old12) mutant that was identified in the Arabidopsis accession Landsberg erecta. The old12 mutant is characterized by a growth defect, spontaneous cell death, plant-defense gene activation, and early senescence. In addition, the old12 phenotype is temperature reversible, thereby exhibiting all characteristics of an autoimmune mutant. Mapping the mutated locus revealed that the old12 phenotype is caused by a mutation in the Lectin Receptor Kinase P2-TYPE PURINERGIC RECEPTOR 2 (P2K2) gene. Interestingly, the P2K2 allele from Landsberg erecta is conserved among Brassicaceae. P2K2 has been implicated in pathogen tolerance and sensing extracellular ATP. The constitutive activation of defense responses in old12 results in improved resistance against Pseudomonas syringae pv. tomato DC3000.; CONCLUSION: We demonstrate that old12 is an auto-immune mutant and that allelic variation of P2K2 contributes to diversity in Arabidopsis immune responses. © 2023. The Author(s).

Additional file 1: Fig. S1. Early-senescence phenotype of old12 under short-day condition. Fig. S2. Visualization of allele frequency by SHOREmap. Fig. S3. Absence of old12 phenotype in p2k2-1. Fig. S4. Comparison of the protein sequence of P2K2 from different accessions. Fig. S5. Conservation of the C-terminal extension of P2K2 in Brassicaceae. Fig. S6. Full blot images for figure 4 Fig. S7. Tissue-specific expression of P2K2 in Col-0. Fig. S8. Crossing of npr1 into the old12 mutant results in leaf bleaching. Table S1. Putative EMS-induced SNPs on Chromosome I. Table S2. qPCR primers used.

Additional file 1: Fig. S1. Transgenic sorghum lines were grown in a PC2 glasshouse. (a) 1 week; (b) 2 weeks; (c) 3 weeks; (d) 5 weeks; (e) 7 weeks; (f) 10 weeks in the glasshouse; (g) mature T×430; (h) mature A5; (f) mature L9. Fig. S2. The Construct Used for Gene Transformation. Stem-specific Promoter: either A1 resulting in high gene expression in the mature stalk or LSG2 resulting in high gene expression in the loading sucrose section of the stalk. Vacuole leading: encoding a propeptide to guide SI gene products to vacuole, where sucrose accumulates. Non-silence target gene: sucrose isomerase without motifs gene silencing in plants. Multiple terminators: three recombined terminators complex to guarantee the proper termination of gene transcription. Fig. S3. PCR screening of sucrose isomerase gene in transgenic LSG2 lines. The agarose gel displayed PCR results of transgenic lines. M: DNA ladder; NC: negative control; Transgenic lines L1, L2, L3, L4, L5, L7, L9, L14, and L16 were positive of the sucrose isomerase gene; Transgenic lines L6, L8, L10, L11, L12, L13,L15, and L17 were negative of the sucrose isomerase gene. Fig. S4. Sugar profile of T1 L9 lines. Sugars, including isomaltulose, were measured 20-day post-anthesis in the middle section of internode 4 (counted from top). L9 is one of the top lines in T0 transgenic lines. L9-2, 9-3, 9-6, 9-7, 9-11, 9-12 are isomaltulose positive samples. Nil-L9-4, 9-8 and 9-9 are null-segregant samples in T1 generation. T×430-1, T×430-2, and T×430-3 are the non-transformed control. Fig. S5. PCR screening of sucrose isomerase gene in T1 lines. The agarose gel displayed PCR results of transgenic lines and controls. M: 1 Kb DNA ladder; Positive A5 T1 progenies: A5-2 and A5-4; Positive L2 T1 progenies: L2-1, L2-3 and L2-6; Positive L9 T1 progenies: L9-2, and L9-4; T×430-1, T×430-2 are non-transgenic control samples; PC: positive plasmid control (LSG2). Table S1. Sugar profile of controls and positive transgenic lines with isomaltulose. Table S2. Sugar profile of F1 hybrid lines of R9188 X L9.

Additional file 2: Table S2. Feature comparisons between two versions.

Additional file 2: Figure S2. Significant loci detected in multiple amino acid traits. A total of 47 SNPs representing 40 loci were identified in at least two amino acid traits. All SNPs within a 40 kb region defines a locus.

Additional file 1: Figure S1. A radar chart showing the distribution of average values of grain quality traits across different sorghum usage groups. The numbers on the chart are the average values of each grain quality trait, and the length of lines is proportional to these averages. Different line colours represent different usage groups.

The process of leaf senescence consists of the final stage of leaf development. It has evolved as a mechanism to degrade macromolecules and micronutrients and remobilize them to other developing parts of the plant; hence it plays a central role for the survival of plants and crop production. During senescence, a range of physiological, morphological, cellular, and molecular events occur, which are generally referred to as the senescence syndrome that includes several hallmarks such as visible yellowing, loss of chlorophyll and water content, increase of ion leakage and cell death, deformation of chloroplast and cell structure, as well as the upregulation of thousands of so-called senescence-associated genes (SAGs) and downregulation of photosynthesis-associated genes (PAGs). This chapter is devoted to methods characterizing the onset and progression of leaf senescence at the morphological, physiological, cellular, and molecular levels. Leaf senescence normally progresses in an age-dependent manner but is also induced prematurely by a variety of environmental stresses in plants. Focused on the hallmarks of the senescence syndrome, a series of protocols is described to asses quantitatively the senescence process caused by developmental cues or environmental perturbations. We first briefly describe the senescence process, the events associated with the senescence syndrome, and the theories and methods to phenotype senescence. Detailed protocols for monitoring senescence in planta and in vitro, using the whole plant and the detached leaf, respectively, are presented. For convenience, most of the protocols use the model plant species Arabidopsis and rice, but they can be easily extended to other plants.

The effect of ethylene exposure time on leaf senescence was studied in Arabidopsis accessions Ler-0, Col-0 and Ws-0 and in several old (onset of leaf death) mutants representing different genetic loci. Leaf senescence was observed in 24-day-old plants exposed to ethylene for 3 to 16 days. For ethylene treatments up to 12 days, a longer ethylene exposure time resulted in more senescing leaves in wild type plants. However, a 16-day ethylene treatment reduced senescence symptoms. old mutants differentially responded to varied ethylene exposure times. In old3, old9, old12 and old14 mutants, the same number of leaves turned yellow, regardless of the ethylene exposure time. In old5 and old13, increasing ethylene exposure time from 6 to 16 days resulted in the same number of yellow leaves, but less leaves yellowed in a 3-day treatment. The amounts of senescing leaves in old1-1 and old11 mutants decreased with increases in ethylene exposure time from 6 to 16 days. Thus, multiple OLD genes may act to restrict the induction of senescence by ethylene in an ethylene exposure time-dependent manner. The data substantiate the notion that there is a complex interaction between leaf age and ethylene involving multiple genetic loci.

Cell cycle activities are initiated following imbibition of non-dormant seeds. However, it is not known whether cell cycle related events other than DNA replication also remain suppressed in imbibed dormant seeds. The objective of this study was to demonstrate that the transitions between the non-dormant and dormant (both primary and secondary) states are reflected in cell cycle events, such as DNA replication and the changing patterns of the microtubular cytoskeleton involved in the processes of growth and development. The present studies were conducted on seeds from tomato (Lycopersicon esculentum cv. Moneymaker) that possessed primary dormancy or were manipulated to attain secondary dormancy. In addition, a non-dormant abscisic acid (ABA)-deficient mutant, sitw, was used. DNA replication, as measured by flow cytometry, and -tubulin accumulation, analysed by immunoblotting, were compared with immunocytological studies of active DNA synthesis and microtubular cytoskeleton formation. It is shown that the depth of dormancy, which distinguishes primary and secondary dormancy, may depend on the progression of the cell cycle prior to the induction of dormancy.