Biology subjects

Czymmek, K. J.

Publications and source records attributed to Czymmek, K. J..

3 recordsLinked to original sources

bioRxiv2020

Pre-meiotic, 24-nt reproductive phasiRNAs are abundant in anthers of wheat and barley but not rice and maize

Two classes of pre-meiotic (21-nt) and meiotic (24-nt) phasiRNAs and their patterns of accumulation have been described in maize and rice anthers. Their precise function remains unclear, but some studies have shown that they support male fertility. The important role of phasiRNAs in anthers underpins our current study to their characterization in wheat and barley anthers. In this study, we staged anthers at every 0.2 mm of development for one wheat and two barley varieties. We isolated pre-meiotic (0.2 mm, 0.4 mm and 0.6 mm), meiotic (0.8 mm, 1.0 mm and 1.4 mm) and post-meiotic (1.8 mm) anthers for which we then investigated accumulation patterns of RNAs, including reproductive phasiRNAs. We annotated a total 12,821 and 2,897 PHAS loci in the wheat and barley genomes, respectively. When comparing the total number of PHAS loci in genomes of maize, rice, barley and wheat, we characterized an expansion of reproductive PHAS loci in the genomes of Poaceae subfamilies from Panicoideae to Oryzoideae and to Poideae. In addition to the two classes of pre-meiotic (21-nt) and meiotic (24-nt) phasiRNAs, previously described in maize and rice anthers, we described a group of 24-nt phasiRNAs that accumulate in pre-meiotic anthers. The absence of pre-meiotic 24-nt phasiRNAs in maize and rice suggests a divergence in grass species of the Poideae subfamily. Additionally, we performed a co-expression gene analysis describing the regulation of phasiRNA biogenesis in wheat and barley anthers. We highlight AGO9 and AGO6 as candidate binding partners of pre-meiotic and meiotic 24-nt phasiRNAs, respectively. One sentence summaryIn wheat and barley anthers, 24-nt reproductive phasiRNAs are abundant in both meiotic and pre-meiotic stages.

plant biology↗

bioRxiv2020

Shifting carbon flux from non-transient starch to lipid allows oil accumulation in transgenic tobacco leaves

Plant leaf biomass is composed predominantly of carbohydrate and protein with less than 5% dry weight allocated to lipid and less than 1% of total lipid in the form of triacylglycerols (TAGs). The combined overexpression of multiple genes involved in different aspects of TAG synthesis and stabilization can result in TAG accumulation to over 30% dry weight in tobacco leaves, presumably requiring many metabolic adjustments within plant cells. The metabolic consequences to the combined source and sink capacities of high oil accumulating transgenic tobacco leaves compared to wild-type were inspected across development and photoperiod by utilizing foliar biomass components and 13CO2 flux through central carbon intermediates. Lipid biosynthesis was investigated through assessment of acyl-acyl carrier protein (ACP) pools using a recently derived quantification method that was extended to accommodate isotopic labeling. Lipids accumulated stepwise over plant development in the high-oil leaves, with 13CO2-labeling studies confirming increased carbon flux to lipids. The large increase in lipid content was concurrent with a decrease in foliar starch, with limited contribution from non-sucrose soluble sugars, indicating a redirection of carbon from starch to lipids. Starch accumulated non-transiently with plant age in wild-type leaves, suggesting an inherent capacity for a developmentally-regulated carbon sink in tobacco leaves that may have enabled the programmed altered carbon partitioning to lipids in transgenics. These studies provide insight into the metabolic plasticity of dual source-sink leaves over development and may in part explain recent successful leaf lipid engineering efforts in tobacco. One sentence summaryEngineering high oil accumulation in tobacco leaves is enabled by inherent source-sink plasticity associated with non-transient foliar starch accumulation over development.

plant biology↗

bioRxiv2020

Antifungal symbiotic peptide NCR044.1 exhibits unique structure and multi-faceted mechanisms of action that confer plant protection

NCR044.1 is a 36-amino acid nodule-specific cysteine-rich antimicrobial peptide expressed in the developing nodules of Medicago truncatula. Here, we determined its unique NMR structure to be largely disordered, one four-residue -helix and one three-residue anti-parallel {beta}-sheet stabilized by two disulfide bonds, suggesting it is highly dynamic. NCR044.1 exhibited potent fungicidal activity against multiple plant fungal pathogens. It breached the fungal plasma membrane, bound to multiple phosphoinositides, and induced reactive oxygen species. Time-lapse confocal and super-resolution microscopy revealed strong fungal cell wall binding, penetration of the cell membrane at discrete foci, followed by gradual loss of turgor, and subsequent accumulation in the cytoplasm with elevated levels in nucleoli. Nucleolar localization of NCR044.1 was unique amongst plant antifungal peptides, suggesting its potential interaction with ribosomes and inhibition of translation. Spray-applied NCR044.1 significantly reduced gray mold disease symptoms caused by the fungal pathogen Botrytis cinerea in tomato plants and post-harvest products demonstrating its potential as a spray-on peptide-based biofungicide.

plant biology↗