Prime editing events revealed by next-generation sequencing (NGS). (D) Quantification of prime editing frequencies by PPE3b-V01 at five target sites. (E) Editing events revealed by NGS reads. (F) Schematics of the expression vectors of Plant Prime Editor 3 or 2-Version 2 (PPE3/2-V02). (G-I) Comparison of multiple PBS-RT pairs of different lengths for directing TCA insertion at the OsPDS target site, directing C to A base change at the OsDEP1 target site and directing TGA insertion at the OsDEP1 target site, respectively, by PPE3-V02. (J and K) Validation of prime editing outcomes by NGS at the OsPDS-pegR15, OsDEP1-pegR03, and OsDEP1-pegR10 target sites. (M) Comparison of PPE3-V02 and PPE2-V02 for precise editing at five target sites. (N) PPE2-V02 based prime editing events revealed by NGS for the OsPDS-sgRNA01 3T ins construct (for insertion of a T 3 nt downstream of the PBS). (O) PPE2-V02 based prime editing at another site with multiple PBS-RT pairs of different lengths. The experiments were done in rice protoplasts.Three biological replicates were used to assess the PPE3-V01 system (B-E), and two biological replicates were used to assess PPE3-V02 and PPE2-V02 systems (G-O). Error bars represent standard deviations of the biological replicates. For NGS-based genotyping data presentations (C, E, J, K, L, and N), the sequences (from top to bottom) include the wild-type (WT) sequence (protospacer underlined and PAM in bold), the expected prime editing outcome (Reference), confirmed precise prime editing events matching the expected prime editing outcome (PE_Ref), precise prime editing plus additional single nucleotide polymorphisms (e.g., PE_h01; h stands for haplotype) and deletions resulted from the NHEJ repair. The prime edited DNA nucleotides are highlighted in red.

No abstract

The chloroplast thioredoxins (TRXs) function as messengers of redox signals from ferredoxin to target enzymes. In this work, we studied the regulatory impact of pea (Pisum sativum) TRX-F on the magnesium (Mg) chelatase CHLI subunit and the enzymatic activation of Mg chelatase in vitro and in vivo. In vitro, reduced TRX-F activated the ATPase activity of pea CHLI and enhanced the activity of Mg chelatase reconstituted from the three recombinant subunits CHLI, CHLD, and CHLH in combination with the regulator protein GENOMES UNCOUPLED4 (GUN4). Yeast two-hybrid and bimolecular fluorescence complementation assays demonstrated that TRX-F physically interacts with CHLI but not with either of the other two subunits or GUN4. In vivo, virus-induced TRX-F gene silencing (VIGS-TRX-F) in pea plants did not result in an altered redox state of CHLI. However, simultaneous silencing of the pea TRX-F and TRX-M genes (VIGS-TRX-F/TRX-M) resulted in partially and fully oxidized CHLI in vivo. VIGS-TRX-F/TRX-M plants demonstrated a significant reduction in Mg chelatase activity and 5-aminolevulinic acid synthesizing capacity as well as reduced pigment content and lower photosynthetic capacity. These results suggest that, in vivo, TRX-M can compensate for a lack of TRX-F and that both TRXs act as important redox regulators of Mg chelatase. Furthermore, the silencing of TRX-F and TRX-M expression also affects gene expression in the tetrapyrrole biosynthesis pathway and leads to the accumulation of reactive oxygen species, which may also serve as an additional signal for the transcriptional regulation of photosynthesis-associated nuclear genes.

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Summary Pollution of soil by the heavy metal cadmium (Cd) is a global environmental problem. The glutathione (GSH)‐dependent phytochelatin (PC) synthesis pathway is one of the most important mechanisms contributing to Cd accumulation and tolerance. However, the regulation of this pathway is poorly understood. Here, we identified an Arabidopsis thaliana cadmium‐tolerant dominant mutant xcd1‐D (XVE system‐induced cadmium‐tolerance 1) and cloned XCD1 gene (previously called MAN3), which encodes an endo‐β‐mannanase. Overexpression of MAN3 led to enhanced Cd accumulation and tolerance, whereas loss‐of‐function of MAN3 resulted in decreased Cd accumulation and tolerance. In the presence of estradiol, enhanced Cd accumulation and tolerance in xcd1‐D was associated with GSH‐dependent, Cd‐activated synthesis of PCs, which was correlated with coordinated activation of gene expression. Cd stress‐induced expression of MAN3 and the consequently increased mannanase activity, led to increased mannose content in cell walls. Moreover, mannose treatment not only rescued the Cd‐sensitive phenotype of the xcd1‐2 mutant, but also improved the Cd tolerance of wild‐type plants. Significantly, this mannose‐mediated Cd accumulation and tolerance is dependent on GSH‐dependent PC concentrations via coordinated control of expression of genes involved in PC synthesis. Our results suggest that MAN3 regulates the GSH‐dependent PC synthesis pathway that contributes to Cd accumulation and tolerance in A. thaliana by coordinated control of gene expression.

Cadmium (Cd) extrusion is an important mechanism conferring Cd tolerance by decreasing its accumulation in plants. Previous studies have identified an Arabidopsis ABC transporter, PDR8, as a Cd extrusion pump conferring Cd tolerance. However, the regulation of PDR8 in response to Cd stress is still largely unknown. In this study, we identified an Arabidopsis cadmium-tolerant dominant mutant, designated xcd3-D, from the XVE-tagging T-DNA insertion lines by a gain-of-function genetic screen.The corresponding gene was cloned and shown to encode a nuclear WRKY transcription factor WRKY13. Expression of WRKY13 was induced by Cd stress. Overexpression of WRKY13 resulted in decreased Cd accumulation and enhanced Cd tolerance, whereas loss-of-function of WRKY13 led to increased Cd accumulation and sensitivity. Further analysis showed that WRKY13 activates the transcription of PDR8 by directly binding to its promoter. Genetic analysis indicated that WRKY13 acts upstream of PDR8 to positively regulate Cd tolerance. Our results provide evidence that WRKY13 directly targets PDR8 to positively regulate Cd tolerance in Arabidopsis.

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Hydrogen sulfide (H2S) signaling has been considered a key regulator of plant developmental processes and defenses. In this study, we demonstrate that high levels of H2S inhibit auxin transport and lead to alterations in root system development. H2S inhibits auxin transport by altering the polar subcellular distribution of PIN proteins. The vesicle trafficking and distribution of the PIN proteins are an actin-dependent process. H2S changes the expression of several actin-binding proteins (ABPs) and decreases the occupancy percentage of F-actin bundles in the Arabidopsis roots. We observed the effects of H2S on F-actin in T-DNA insertion mutants of cpa, cpb and prf3, indicating that the effects of H2S on F-actin are partially removed in the mutant plants. Thus, these data imply that the ABPs act as downstream effectors of the H2S signal and thereby regulate the assembly and depolymerization of F-actin in root cells. Taken together, our data suggest that the existence of a tightly regulated intertwined signaling network between auxin, H2S and actin that controls root system development. In the proposed process, H2S plays an important role in modulating auxin transport by an actin-dependent method, which results in alterations in root development in Arabidopsis.