bims-plasge 2025-02-02 papers

Issue of 2025–02–02
five papers selected by
Vera S. Bogdanova, ИЦиГ СО РАН

Plants (Basel). 2025 Jan 16. pii: 247. [Epub ahead of print]14(2):

RAS, a Pentatricopeptide Repeat Protein, Interacts with OsTRX z to Regulate Chloroplast Gene Transcription and RNA Processing.

Zhennan Qiu, Shiyong Wen, Peinan Sun, Dongdong Chen, Chunmiao Wang, Xiliang Song, Liying Xiao, Peiliang Zhang, Dongying Zhao, Cuiping Wen, Peiyan Guan, Xuechu Du, Yinghui Sun, Chenshan Xu, Jian Song.

Thioredoxin z (TRX z) plays a significant role in chloroplast development by regulating the transcription of chloroplast genes. In this study, we identified a pentatricopeptide repeat (PPR) protein, rice albino seedling-lethal (RAS), that interacts with OsTRX z. This interaction was initially discovered by using a yeast two-hybrid (Y2H) screening technique and was further validated through Y2H and bimolecular fluorescence complementation (BiFC) experiments. RAS contains 16 PPR motifs and features a small MutS-related (SMR) domain at its C-terminus. CRISPR/Cas9-generated ras mutants exhibited an albino seedling-lethal phenotype characterized by abnormal chloroplast structures and a significantly reduced chlorophyll content. RAS localizes to the chloroplast and is predominantly expressed in young leaves. Mutations in RAS affect RNA editing at the rpl2, rps14, and ndhA sites, as well as RNA splicing at the rpl2, atpF, and ndhA transcripts within the chloroplast. Furthermore, the expression levels of genes associated with chloroplast formation are altered in the ras mutant. Both OsTRX z and RAS were found to interact with chloroplast signal recognition particle (cpSRP) proteins, indicating that their proper localization within the chloroplast may be dependent on the SRP pathway. Collectively, our findings highlight the critical role of RAS in chloroplast development, as it is involved in RNA processing and the regulation of chloroplast gene expression.

Keywords: PPR; RNA editing; RNA splicing; chloroplast development; rice

DOI: https://doi.org/10.3390/plants14020247

Int J Mol Sci. 2025 Jan 15. pii: 701. [Epub ahead of print]26(2):

Ac/Ds-like Transposon Elements Inserted in ZmABCG2a Cause Male Sterility in Maize.

Le Wang, Saeed Arshad, Taotao Li, Mengli Wei, Hong Ren, Wei Wang, Haiyan Jia, Zhengqiang Ma, Yuanxin Yan.

Using male sterile (MS) lines instead of normal inbred maternal lines in hybrid seed production can increase the yield and quality with lower production costs. Therefore, developing a new MS germplasm is essential for maize hybrid seed production in the future. Here, we reported a male sterility gene ms*-N125, cloned from a newly found MS mutant ms*-N125. This mutant has an underdeveloped tassel that showed impaired glumes and shriveled anthers without pollen grains. The MS locus of ms*-N125 was mapped precisely to a 112-kb-interval on the chromosome 5. This interval contains only three candidate genes, Zm958, Zm959, and Zm960. Sequencing results showed that only candidate Zm960 harbored a 548-bp transposable element (TE) in its 9th exon, and the two other candidate genes were found to have no genetic variations between the mutant and wild type (WT). Thus, Zm960 is the only candidate gene for male sterility of the mutant ms*-N125. In addition, we screened another recessive MS mutant, ms*-P884, which exhibited similar male sterility phenotypes to ms*-N125. Sequencing Zm960 in ms*-P884 showed a 600-bp TE located in its 2nd exon. Zm960 encodes an ATP-binding cassette in the G subfamily of ABC (ABCG) transporters, ZmABCG2a, with both mutants which harbored an Ac/Ds-like transposon in each. To verify the function of ZmABCG2a for male sterility further, we found an ethyl methanesulfonate (EMS) mutant, zmabcg2a*, which displayed male sterility and tassel phenotypes highly similar to ms*-N125 and ms*-P884, confirming that ZmABCG2a must be the gene for male sterility in maize. In addition, the results of lipid metabolome analysis of ms*-N125 young tassels showed that the total lipid content of the mutant was significantly lower than that of the WT, with 15 subclasses of lipids, including PE (phosphatidylethanolamine), PC (phosphatidylcholine), DG (digalactosyldiacylglycerols), and MGDG (monogalactosyldiacylglycerol) which were significantly down-regulated in the ms*-N125 mutant versus its wild type. In summary, we identified alternate mutations of the ZmABCG2a gene, which may be a potential germplasm for hybrid seed production in maize.

Keywords: ZmABCG2a; maize (Zea mays); mutant ms*-N125; mutant ms*-P884; seed production

DOI: https://doi.org/10.3390/ijms26020701

Curr Biol. 2025 Jan 21. pii: S0960-9822(24)01705-6. [Epub ahead of print]

The atypical proteome of mitochondria from mature pollen grains.

Clément Boussardon, Matthieu Simon, Chris Carrie, Matthew Fuszard, Etienne H Meyer, Françoise Budar, Olivier Keech.

To propagate their genetic material, flowering plants rely on the production of large amounts of pollen grains that are capable of germinating on a compatible stigma. Pollen germination and pollen tube growth are thought to be extremely energy-demanding processes. This raises the question of whether mitochondria from pollen grains are specifically tuned to support this developmental process. To address this question, we isolated mitochondria from both mature pollen and floral buds using the isolation of mitochondria tagged in specific cell-type (IMTACT) strategy and examined their respective proteomes. Strikingly, mitochondria from mature pollen grains have lost many proteins required for genome maintenance, gene expression, and translation. Conversely, a significant accumulation of proteins associated with the tricarboxylic acid (TCA) cycle, the electron transport chain (ETC), and Ca2+ homeostasis was observed. This supports the current model in which pollen requires large quantities of ATP for tube growth but also identifies an unexpected depletion of the gene expression machinery, aligned with the fact that the mitochondrial genome is actively degraded during pollen maturation. Altogether, our results uncover that mitochondria from mature pollen grains are strategically prepared for action by increasing their respiratory capacity and dismantling their gene expression machinery, which raises new questions about the assembly of respiratory complexes in pollen mitochondria, as they rely on the integration of proteins coded by the nuclear and mitochondrial genomes. In addition, the approach described here opens a new range of possibilities for studying mitochondria during pollen development and in pollen-specific mitochondrial events.

DOI: https://doi.org/10.1016/j.cub.2024.12.037

Mol Plant. 2025 Jan 28. pii: S1674-2052(25)00042-5. [Epub ahead of print]

Chloroplast State Transitions Modulate Nuclear Genome Stability via Cytokinin Signaling in Arabidopsis.

Yajun Zeng, Sujuan Duan, Yawen Wang, Zhifeng Zheng, Zeyi Wu, Meihui Shi, Manchun Wang, Lan Jiang, Xue Li, Hong-Bin Wang, Hong-Lei Jin.

Activities of the chloroplasts and nucleus are coordinated by retrograde signaling, which has crucial roles in plant development and environmental adaptation. However, the connection between chloroplast status and nuclear genome stability is not well understood. Chloroplast state transitions allow the plant to balance the absorption capacity of the photosystems in an environment in which the light quality was changing. Here we demonstrate that abnormal chloroplast state transitions lead to instability of the nuclear genome and impaired plant growth. We observed increased DNA damage in the state transition-defective Arabidopsis (Arabidopsis thaliana) mutant stn7; this damage was triggered by cytokinin accumulation and activation of cytokinin signaling. We propose that cytokinin signaling promotes the competitive association of ARABIDOPSIS RESPONSE REGULATOR 10 (ARR10) with PROLIFERATING CELLULAR NUCLEAR ANTIGEN 1/2 (PCNA1/2), thereby inhibiting the binding of PCNA1/2 to nuclear DNA. This affects DNA replication, leading to replication-dependent genome instability. Treatment with 2,5-dibromo-3-methyl-6-isopropylbenzoquinone, which simulates the reduction of the plastoquinone pool during abnormal state transitions, increased the accumulation of ARABIDOPSIS HISTIDINE-CONTAINING PHOSPHOTRANSMITTER 1, a phosphotransfer protein involved in cytokinin signaling, and promoted the interaction of ARR10 with PCNA1/2, leading to DNA damage. These findings highlight the role of cytokinin signaling in coordinating chloroplast function and nuclear genome integrity during plant acclimation to environmental changes.

Keywords: Chloroplast state transitions; cytokinin signaling; nuclear genome stability

DOI: https://doi.org/10.1016/j.molp.2025.01.021

Mol Biol Evol. 2025 Jan 30. pii: msaf025. [Epub ahead of print]

Fungal-derived tRNAs are expressed and aminoacylated in orchid mitochondria.

Jessica M Warren, Luis F Ceriotti, M Virginia Sanchez-Puerta, Daniel B Sloan.

Plant mitochondrial genomes (mitogenomes) experience remarkable levels of horizontal gene transfer (HGT), including the recent discovery that orchids anciently acquired DNA from fungal mitogenomes. Thus far, however, there is no evidence that any of the genes from this interkingdom HGT are functional in orchid mitogenomes. Here, we applied a specialized sequencing approach to the orchid Corallorhiza maculata and found that some fungal-derived tRNA genes in the transferred region are transcribed, post-transcriptionally modified, and aminoacylated. In contrast, all the transferred protein-coding sequences appear to be pseudogenes. These findings show that fungal HGT has altered the composition of the orchid mitochondrial tRNA pool and suggest that these foreign tRNAs function in translation. The exceptional capacity of tRNAs for HGT and functional replacement is further illustrated by the diversity of tRNA genes in the C. maculata mitogenome, which also include genes of plastid and bacterial origin in addition to their native mitochondrial counterparts.

DOI: https://doi.org/10.1093/molbev/msaf025