Plastid and mitochondrial RNAs in vascular plants are subjected to cytidine‐to‐uridine editing. The model plant species
The enzyme carbonic anhydrase (CA), which catalyzes the interconversion of bicarbonate with carbon dioxide (CO2) and water, has been hypothesized to play a role in C3photosynthesis. We identified two tobacco stromal CAs, β-CA1 and β-CA5, and produced CRISPR/Cas9 mutants affecting their encoding genes. While single knockout lines
- Award ID(s):
- 1642386
- NSF-PAR ID:
- 10286431
- Publisher / Repository:
- Proceedings of the National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 118
- Issue:
- 33
- ISSN:
- 0027-8424
- Page Range / eLocation ID:
- Article No. e2107425118
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Arabidopsis thaliana (Arabidopsis) has two nuclear‐encoded plastid‐targeted organelle RNA recognition motif (ORRM) proteins: ORRM1 and ORRM6. In theorrm1 mutant, 21 plastid RNA editing sites were affected but none are essential to photosynthesis. In theorrm6 mutants, two plastid RNA editing sites were affected:psbF ‐C77 andaccD ‐C794. BecausepsbF encodes the β subunit of cytochromeb 559in photosystem II, which is essential to photosynthesis, theorrm6 mutants were much smaller than the wild type. In addition, theorrm6 mutants had pale green leaves and reduced photosynthetic efficiency. To investigate the functional relationship between ORRM1 and ORRM6, we generatedorrm1 orrm6 double homozygous mutants. Morphological and physiological analyses showed that theorrm1 orrm6 double mutants had a smaller plant size, reduced chlorophyll contents, and decreased photosynthetic efficiency, similar to theorrm6 single mutants. Although theorrm1 orrm6 double mutants adopted the phenotype of theorrm6 single mutants, the total number of plastid RNA editing sites affected in theorrm1 orrm6 double mutants was the sum of the sites affected in theorrm1 andorrm6 single mutants. These data suggest that ORRM1 and ORRM6 are in charge of distinct sets of plastid RNA editing sites and that simultaneous mutations inORRM1 andORRM6 genes do not cause additional reduction in editing extent at other plastid RNA editing sites. -
Maize ANT1 modulates vascular development, chloroplast development, photosynthesis, and plant growthnull (Ed.)Arabidopsis AINTEGUMENTA (ANT), an AP2 transcription factor, is known to control plant growth and floral organogenesis. In this study, our transcriptome analysis and in situ hybridization assays of maize embryonic leaves suggested that maize ANT1 (ZmANT1) regulates vascular development. To better understand ANT1 functions, we determined the binding motif of ZmANT1 and then showed that ZmANT1 binds the promoters of millet SCR1 , GNC , and AN3 , which are key regulators of Kranz anatomy, chloroplast development, and plant growth, respectively. We generated a mutant with a single-codon deletion and two frameshift mutants of the ANT1 ortholog in the C4 millet Setaria viridis by the CRISPR/Cas9 technique. The two frameshift mutants displayed reduced photosynthesis efficiency and growth rate, smaller leaves, and lower grain yields than wild-type (WT) plants. Moreover, their leaves sporadically exhibited distorted Kranz anatomy and vein spacing. Conducting transcriptomic analysis of developing leaves in the WT and the three mutants we identified differentially expressed genes (DEGs) in the two frameshift mutant lines and found many down-regulated DEGs enriched in photosynthesis, heme, tetrapyrrole binding, and antioxidant activity. In addition, we predicted many target genes of ZmANT1 and chose 13 of them to confirm binding of ZmANT1 to their promoters. Based on the above observations, we proposed a model for ANT1 regulation of cell proliferation and leaf growth, vascular and vein development, chloroplast development, and photosynthesis through its target genes. Our study revealed biological roles of ANT1 in several developmental processes beyond its known roles in plant growth and floral organogenesis.more » « less
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SUMMARY Cytokinin has strong connections to development and a growing role in the abiotic stress response. Here we show that CYTOKININ RESPONSE FACTOR 2 (CRF2) is additionally involved in the salt (NaCl) stress response. CRF2 promoter‐GUS expression indicates CRF2 involvement in the response to salt stress as well as the previously known cytokinin response. Interestingly, CRF2 mutant seedlings are quite similar to the wild type (WT) under non‐stressed conditions yet have many distinct changes in response to salt stress. Cytokinin levels measured by liquid chromatography–tandem mass spectrometry (LC‐MS/MS) that increased in the WT after salt stress are decreased in
crf2 , potentially from CRF2 regulation of cytokinin biosynthesis genes. Ion content measured by inductively coupled plasma optical emission spectrometry (ICP‐OES) was increased in the WT for Na, K, Mn, Ca and Mg after salt stress, whereas the corresponding Ca and Mg increases are lacking incrf2 . Many genes examined by RNA‐seq analysis were altered transcriptionally by salt stress in both the WT andcrf2 , yet interestingly approximately one‐third of salt‐modifiedcrf2 transcripts (2655) showed unique regulation. Different transcript profiles for salt stress incrf2 compared with the WT background was further supported through an examination of co‐expressed genes by weighted gene correlation network analysis (WGCMA) and principal component analysis (PCA). Additionally, Gene Ontology (GO) enrichment terms found from salt‐treated transcripts revealed most photosynthesis‐related terms as only being affected incrf2 , leading to an examination of chlorophyll levels and the efficiency of photosystem II (via the ratio of variable fluorescence to maximum fluorescence,F v/F m) as well as physiology after salt treatment. Salt stress‐treatedcrf2 plants had both reduced chlorophyll levels and lowerF v/F mvalues compared with the WT, suggesting that CRF2 plays a role in the modulation of salt stress responses linked to photosynthesis. -
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Abstract Periphyton communities associated with submerged plant detritus contain interacting autotrophic and heterotrophic microbes, and are sites of extracellular enzymatic activity. The strength and nature of these interactions might be expected to change over time as microbial communities develop on plant litter. Microbial interactions and enzymatic activity can be altered by nutrient availability, suggesting that litter stoichiometry could also affect these phenomena.
We grew wetland plants under ambient and nutrient‐enriched conditions to generate plant litter of differing nutrient content. In two experiments, we investigated: (1) the influence of algal photosynthesis on fungal and bacterial production and the activities of four extracellular enzymes throughout a 54‐day period of microbial colonisation and growth; and (2) the influence of litter stoichiometry on these relationships.
Ambient and nutrient‐enriched standing‐dead plant litter was collected and then submerged in wetland pools to allow for natural microbial colonisation and growth. Litter samples were periodically retrieved and transported to the laboratory for experiments manipulating photosynthesis using the photosystem II inhibitor DCMU (which effectively prevents algal photosynthetic activity). Algal (14C‐bicarbonate), bacterial (3H‐leucine), and fungal (14C‐acetate) production, and β‐glucosidase, β‐xylosidase, leucine aminopeptidase, and phosphatase activities (MUF‐ or AMC‐labelled fluorogenic substrates) were measured under conditions of active and inhibited algal photosynthesis.
Photosynthesis stimulated overall fungal and bacterial production in both experiments, although the strength of stimulation varied amongst sampling dates. Phosphatase activity was stimulated by photosynthesis during the first, but not the second, experiment. No other enzymatic responses to short‐term photosynthesis manipulations were observed.
Microbial communities on high‐nutrient litter occasionally showed increased extracellular enzyme activity, fungal growth rates, and bacterial production compared to communities on non‐enriched litter, but algal and fungal production were not affected. Litter stoichiometry had no effects on fungal, bacterial, or enzymatic responses to photosynthesis, but the mean enzyme vector analysis angle (a measure of P‐ versus N‐acquiring enzyme activity) was positively correlated to litter N:P, suggesting that elevated litter N:P led to an increase in the relative activity of P‐acquiring enzymes.
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Summary High concentrations of dissolved inorganic carbon in stems of herbaceous and woody C3plants exit leaves in the dark. In the light, C3species use a small portion of xylem‐transported CO2for leaf photosynthesis. However, it is not known if xylem‐transported CO2will exit leaves in the dark or be used for photosynthesis in the light in Kranz‐type C4plants.
Cut leaves of
Amaranthus hypochondriacus were placed in one of three solutions of [NaH13CO3] dissolved in KCl water to measure the efflux of xylem‐transported CO2exiting the leaf in the dark or rates of assimilation of xylem‐transported CO2* in the light, in real‐time, using a tunable diode laser absorption spectroscope.In the dark, the efflux of xylem‐transported CO2increased with increasing rates of transpiration and [13CO2*]; however, rates of13Ceffluxin
A. hypochondriacus were lower compared to C3species. In the light,A. hypochondriacus fixed nearly 75% of the xylem‐transported CO2supplied to the leaf.Kranz anatomy and biochemistry likely influence the efflux of xylem‐transported CO2out of cut leaves of
A. hypochondriacus in the dark, as well as the use of xylem‐transported CO2* for photosynthesis in the light. Thus increasing the carbon use efficiency of Kranz‐type C4species over C3species.
