S-RNase is the female determinant of self-incompatibility (SI) in pear (). After translocation to the pollen tube, S-RNase degrades rRNA and induces pollen tube death in an -haplotype-specific manner. In this study, we found that the actin cytoskeleton is a target of S-RNase (PbrS-RNase) and uncovered a mechanism that involves phosphatidic acid (PA) and protects the pollen tube from PbrS-RNase cytotoxicity. PbrS-RNase interacts directly with PbrActin1 in an -haplotype-independent manner, causing the actin cytoskeleton to depolymerize and promoting programmed cell death in the self-incompatible pollen tube. Pro-156 of PbrS-RNase is essential for the PbrS-RNase-PbrActin1 interaction, and the actin cytoskeleton-depolymerizing function of PbrS-RNase does not require its RNase activity. PbrS-RNase cytotoxicity enhances the expression of phospholipase D (PbrPLDδ1), resulting in increased PA levels in the incompatible pollen tube. PbrPLDδ1-derived PA initially prevents depolymerization of the actin cytoskeleton elicited by PbrS-RNase and delays the SI signaling that leads to pollen tube death. This work provides insights into the orchestration of the S-RNase-based SI response, in which increased PA levels initially play a protective role in incompatible pollen, until sustained PbrS-RNase activity reaches the point of no return and pollen tube growth ceases.
BackgroundLeucine-rich repeat receptor-like protein kinase (LRR-RLK) is the largest gene family of receptor-like protein kinases (RLKs) and actively participates in regulating the growth, development, signal transduction, immunity, and stress responses of plants. However, the patterns of LRR-RLK gene family evolution in the five main Rosaceae species for which genome sequences are available have not yet been reported. In this study, we performed a comprehensive analysis of LRR-RLK genes for five Rosaceae species: Fragaria vesca (strawberry), Malus domestica (apple), Pyrus bretschneideri (Chinese white pear), Prunus mume (mei), and Prunus persica (peach), which contained 201, 244, 427, 267, and 258 LRR-RLK genes, respectively.ResultsAll LRR-RLK genes were further grouped into 23 subfamilies based on the hidden Markov models approach. RLK-Pelle_LRR-XII-1, RLK-Pelle_LRR-XI-1, and RLK-Pelle_LRR-III were the three largest subfamilies. Synteny analysis indicated that there were 236 tandem duplicated genes in the five Rosaceae species, among which subfamilies XII-1 (82 genes) and XI-1 (80 genes) comprised 68.6%.ConclusionsOur results indicate that tandem duplication made a large contribution to the expansion of the subfamilies. The gene expression, tissue-specific expression, and subcellular localization data revealed that LRR-RLK genes were differentially expressed in various organs and tissues, and the largest subfamily XI-1 was highly expressed in all five Rosaceae species, suggesting that LRR-RLKs play important roles in each stage of plant growth and development. Taken together, our results provide an overview of the LRR-RLK family in Rosaceae genomes and the basis for further functional studies.Electronic supplementary materialThe online version of this article (10.1186/s12864-017-4155-y) contains supplementary material, which is available to authorized users.
COR27 and COR28 encode nighttime repressors integrating Arabidopsis circadian clock and cold response FA Summary It was noted that circadian components function in plant adaptation to diurnal temperature cycles and freezing tolerance. Our genome-wide transcriptome analysis revealed that evening-phased COR27 and COR28 mainly repress the transcription of clockassociated evening genes PRR5, ELF4 and cold-responsive genes. Chromatin immunoprecipitation indicated that CCA1 is recruited to the site containing EE elements of COR27 and COR28 promoters in a temperaturedependent way. Further genetic analysis shows COR28 is essential for the circadian function of PRR9 and PRR7. Together, our results support a role of COR27 and COR28 as nighttime repressors integrating circadian clock and plant cold stress responses.Functional clocks confer plants with fitness advantages in their stationary life, including enhanced photosynthesis and vegetative biomass, growth vigor in hybrids and allopolyploids, timely responses to pathogen, cold stress tolerance, photoperiodic flowering, and hormone signaling responses and other agronomic traits (Greenham and McClung 2015; Seo and Mas 2015). The Arabidopsis circadian clock, like the circadian clock found in many other model organisms, is composed of multiple interlocked transcriptional/translational feedback loops (TTFLs). Circadian-associated genes PSEU-DORESPONSE REGULATOR PRR9, PRR7, PRR5, CIRCADIAN CLOCK ASSOCIATED1 (CCA1), LATE ELONGATED HYPO-COTYL (LHY), LUX ARRHYTHMO (LUX), GIGANTEA (GI) and TIMING OF CAB EXPRESSION1 (TOC1, also called PRR1) play critical roles in plant cold responses (Hsu and Harmer 2014). Transcription of Cold-inducible C-repeat (CRT) /dehydration-responsive binding factors CBF1, CBF2, and CBF3 are upregulated in triple mutant prr9-11 prr7-10 prr5-10 (d975). Overexpression of CCA1a isoform results in higher levels of CBF1-3 and GI transcripts (Seo et al. 2012). Temperature-associated alternative splicing of CCA1, LHY, PRR9, PRR7, PRR5, PRR3, TOC1 mediate responses of circadian clock to diurnal temperature changes; especially CCA1b isoform modulates temperature signaling into clock and CCA1a isoform contributes to plant freezing tolerance (James et al. 2012; Seo et al. 2012). Recent study has established preliminary feedback of cold signaling to circadian clock; CBF1 can directly bind to the promoter of LUX, and coldacclimated lux mutants are sensitive to freezing stress (Chow et al. 2014). Despite the importance of the crosstalk between cold-responsive genes in planta, and that the control of low temperature-stress response is one of great interest for circadian research, a known comprehensive architecture of these interactions is still lacking (Bieniawska et al. 2008; Espinoza et al. 2010; Eriksson and Webb 2011; Keily et al. 2013).To identify new evening components contributing to the Arabidopsis circadian transcriptional network, we examined three online platforms of genome-wide expression profiles, NASCArrays (http://affymetrix. arabidopsis.info, closed),...
Plant roots are the first parts of plants to face drought stress (DS), and thus root modification is important for plants to adapt to drought. We hypothesized that the roots of arbuscular mycorrhizal (AM) plants exhibit better adaptation in terms of morphology and phytohormones under DS. Trifoliate orange seedlings inoculated with Diversispora versiformis were subjected to well-watered (WW) and DS conditions for 6 weeks. AM seedlings exhibited better growth performance and significantly greater number of 1st, 2nd, and 3rd order lateral roots, root length, area, average diameter, volume, tips, forks, and crossings than non-AM seedlings under both WW and DS conditions. AM fungal inoculation considerably increased root hair density under both WW and DS and root hair length under DS, while dramatically decreased root hair length under WW but there was no change in root hair diameter. AM plants had greater concentrations of indole-3-acetic acid, methyl jasmonate, nitric oxide, and calmodulin in roots, which were significantly correlated with changes in root morphology. These results support the hypothesis that AM plants show superior adaptation in root morphology under DS that is potentially associated with indole-3-acetic acid, methyl jasmonate, nitric oxide, and calmodulin levels.
The allelopathic potential of rice varieties will likely have a great impact on paddy weed control if integrated with cultural management options and application of low doses of herbicides. Therefore, it is feasible to reduce herbicide input in paddies if allelopathic rice is grown under integrated cultural management practices.
Coxiella burnetii is an obligate intracellular Gram-negative bacterium that causes acute Q fever and chronic infections in humans. A killed, whole cell vaccine is efficacious, but vaccination can result in severe local or systemic adverse reactions. Although T cell responses are considered pivotal for vaccine derived protective immunity, the epitope targets of CD4+ T cell responses in C. burnetii vaccination have not been elucidated. Since mapping CD4+ epitopes in a genome with over 2,000 ORFs is resource intensive, we focused on 7 antigens that were known to be targeted by antibody responses. 117 candidate peptides were selected from these antigens based on bioinformatics predictions of binding to the murine MHC class II molecule H-2 IAb. We screened these peptides for recognition by IFN-γ producing CD4+ T cell in phase I C. burnetii whole cell vaccine (PI-WCV) vaccinated C57BL/6 mice and identified 8 distinct epitopes from four different proteins. The identified epitope targets account for 8% of the total vaccination induced IFN-γ producing CD4+ T cells. Given that less than 0.4% of the antigens contained in C. burnetii were screened, this suggests that prioritizing antigens targeted by antibody responses is an efficient strategy to identify at least a subset of CD4+ targets in large pathogens. Finally, we examined the nature of linkage between CD4+ T cell and antibody responses in PI-WCV vaccinated mice. We found a surprisingly non-uniform pattern in the help provided by epitope specific CD4+ T cells for antibody production, which can be specific for the epitope source antigen as well as non-specific. This suggests that a complete map of CD4+ response targets in PI-WCV vaccinated mice will likely include antigens against which no antibody responses are made.
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