Brassinosteroids (
The ability to edit plant genomes through gene targeting (
- NSF-PAR ID:
- 10033348
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- The Plant Journal
- Volume:
- 89
- Issue:
- 6
- ISSN:
- 0960-7412
- Page Range / eLocation ID:
- p. 1251-1262
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract BRs ) are essential plant growth‐promoting hormones involved in many processes throughout plant development, from seed germination to flowering time. SinceBRs do not undergo long‐distance transport, cell‐ and tissue‐specific regulation of hormone levels involves both biosynthesis and inactivation. To date, tenBR ‐inactivating enzymes, with at least five distinct biochemical activities, have been experimentally identified in the model plantArabidopsis thaliana . Epigenetic interactions betweenT‐DNA insertion alleles and genetic linkage have hindered analysis of higher‐order null mutants in these genes. A previous study demonstrated that thebas1‐2 sob7‐1 ben1‐1 triple‐null mutant could not be characterized due to epigenetic interactions between the exonicT‐DNA insertions inbas1‐2 andsob7‐1, causing the intronicT‐DNA insertion ofben1‐1 to revert to a partial loss‐of‐function allele. We usedCRISPR‐Cas9 genome editing to avoid this problem and generated thebas1‐2 sob7‐1 ben1‐3 triple‐null mutant. This triple‐null mutant resulted in an additive seedling long‐hypocotyl phenotype. We also uncovered a role forBEN1 BR ‐inactivation in seedling cotyledon petiole elongation that was not observed in the singleben1‐2 null mutant but only in the absence of bothBAS1 SOB7 BEN1 BAS1 SOB7 BAS1 BEN1 ,SOB7 -
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Abstract The arrival to the
U nitedS tates of theA fricanized honey bee, a hybrid betweenE uropean subspecies and theA frican subspeciesA pis mellifera scutellataA frican andE uropean lineages in a feral population inS outhT exas. An 11‐year survey of this population (1991–2001) showed that mitochondrial haplotype frequencies changed drastically over time from a resident population of eastern and western European maternal ancestry, to a population dominated by theA frican haplotype. A subsequent study of the nuclear genome showed that theA fricanization process included bidirectional gene flow between European and Africanized honey bees, giving rise to a new panmictic mixture ofA . m. scutellata‐A. m. scutellata maternal ancestry, and three were of western European maternal ancestry. No colonies of eastern European maternal ancestry were detected, although they were present in the earlier samples. NuclearDNA revealed little change in the introgression ofA . m. scutellata -
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Premise Male gametophytes of most seed plants deliver sperm to eggs via a pollen tube. Pollen tube growth rates (
PTGR s) of angiosperms are exceptionally rapid, a pattern attributed to more effective haploid selection under stronger pollen competition. Paradoxically, whole genome duplication (WGD ) has been common in angiosperms but rare in gymnosperms. Pollen tube polyploidy should initially acceleratePTGR because increased heterozygosity and gene dosage should increase metabolic rates. However, polyploidy should also independently increase tube cell size, causing more work which should decelerate growth. We asked how genome size changes have affected the evolution of seed plantPTGR s.Methods We assembled a phylogenetic tree of 451 species with known
PTGR s. We then used comparative phylogenetic methods to detect effects of neo‐polyploidy (within‐genus origins),DNA content, andWGD history onPTGR , and correlated evolution ofPTGR andDNA content.Results Gymnosperms had significantly higher
DNA content and slowerPTGR optima than angiosperms, and theirPTGR andDNA content were negatively correlated. For angiosperms, 89% of model weight favored Ornstein‐Uhlenbeck models with a fasterPTGR optimum for neo‐polyploids, whereasPTGR andDNA content were not correlated. For within‐genus and intraspecific‐cytotype pairs,PTGR s of neo‐polyploids < paleo‐polyploids.Conclusions Genome size increases should negatively affect
PTGR when genetic consequences ofWGD s are minimized, as found in intra‐specific autopolyploids (low heterosis) and gymnosperms (fewWGD s). But in angiosperms, the higherPTGR optimum of neo‐polyploids and non‐negativePTGR ‐DNA content correlation suggest that recurrentWGD s have caused substantialPTGR evolution in a non‐haploid state. -
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Summary In plants, 24 nucleotide long heterochromatic si
RNA s (het‐siRNA s) transcriptionally regulate gene expression byRNA ‐directedDNA methylation (RdDM ). The biogenesis of most het‐siRNA s depends on the plant‐specificRNA polymeraseIV (PolIV ), andARGONAUTE 4 (AGO 4) is a major het‐siRNA effector protein. Through genome‐wide analysis ofsRNA ‐seq data sets, we found thatAGO 4RNA s. The accumulation ofAGO 4RNA s also requires several factors known to participate in the effector portion of the RdDM pathway, includingRNA POLYMERASE V (POL V),DOMAINS REARRANGED METHYLTRANSFERASE 2 (DRM 2) andSAWADEE HOMEODOMAIN HOMOLOGUE 1 (SHH 1). Like manyAGO proteins,AGO 4 is an endonuclease that can ‘slice’RNA s. We found that a slicing‐defectiveAGO 4 was unable to fully recoverAGO 4‐RNA accumulation fromago4 mutant plants. Collectively, our data suggest thatAGO 4RNA s are secondary siRNA s dependent on the prior activity of the RdDM pathway at certain loci. -
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Summary Actin filament assembly in plants is a dynamic process, requiring the activity of more than 75 actin‐binding proteins. Central to the regulation of filament assembly and stability is the activity of a conserved family of actin‐depolymerizing factors (
ADF s), whose primarily function is to regulate the severing and depolymerization of actin filaments. In recent years, the activity ofADF proteins has been linked to a variety of cellular processes, including those associated with response to stress. Herein, a wheatADF Ta was identified and characterized.ADF 4,Ta encodes a 139‐amino‐acid protein containing five F‐actin‐binding sites and two G‐actin‐binding sites, and interacts with wheat (ADF 4Triticum aestivum ) Actin1 (TaACT 1),in planta . Following treatment of wheat, separately, with jasmonic acid, abscisic acid or with the avirulent race,CYR 23, of the stripe rust pathogenPuccinia striiformis f. sp.tritici , we observed a rapid induction in accumulation ofTa ADF 4mRNA . Interestingly, accumulation ofTa ADF 4mRNA was diminished in response to inoculation with a virulent race,CYR 31. Silencing ofTa resulted in enhanced susceptibility toADF 4CYR 23, demonstrating a role forTa in defense signaling. Using a pharmacological‐based approach, coupled with an analysis of host response to pathogen infection, we observed that treatment of plants with the actin‐modifying agent latrunculin B enhanced resistance toADF 4CYR 23, including increased production of reactive oxygen species and enhancement of localized hypersensitive cell death. Taken together, these data support the hypothesis thatTa ADF 4 positively modulates plant immunity in wheat via the modulation of actin cytoskeletal organization.
