Ultraviolet-B radiation has a dual effect on plants, acting both as a developmental cue and a source of genetic stress. Plants must balance growth, DNA repair, cell division, and damage mitigation. Oxidation Resistance (OXR) proteins are evolutionarily conserved, TLDc-domain-containing mitochondrial proteins that link redox homeostasis to nuclear stress responses, which makes them strong candidates to coordinate the plant response to UV-B. This study highlights that the Arabidopsis protein AtOXR2 and its sunflower orthologue, HaOXR2, are critical for enhancing plant tolerance to UV-B radiation. Transgenic plants overexpressing AtOXR2 or HaOXR2 showed improved growth under UV-B radiation, with reduced inhibition of leaf, hypocotyl, and root development. Additionally, these plants exhibited reduced meristematic cell death and fewer cyclobutane pyrimidine dimers, a major form of UV-B-induced DNA damage. In vivo analysis using the PlaCCI reporter revealed that while wild-type plants arrest in the G2/M phase after UV-B, OXR2-overexpressing lines maintain a G1/S-enriched cell-cycle profile, suggesting reduced perception of UV-B damage. Furthermore, these plants showed elevated expression of genes associated with light signalling, DNA repair, and cell-cycle checkpoints, along with increased accumulation of protective phenolic and flavonoid compounds. Loss-of-function oxr2 mutants did not show reduced UV-B sensitivity, likely due to compensatory upregulation of compensatory mechanisms involving other OXR family members. Comparative transcriptomic analyses support a two-module model where OXR2 pre-activates the canonical UV-B damage response, thereby establishing OXR2 as an agronomic determinant of UV-B tolerance.
D. Eusebi, Pablo Torti, Evelyn Becerra-Agudelo et al.· Plant physiology and biochem...· 0 citations
Plants produce diverse small interfering RNA (siRNA) molecules that modulate development, environmental responses, and immunity. Although transgene-derived siRNAs are traditionally viewed as mediators of gene silencing, whether they can actively regulate endogenous host pathways remains largely unexplored. Previously obtained Arabidopsis, wheat, and soybean plants expressing the sunflower gene encoding the transcription factor HaHB4 exhibited water deficit tolerance. Here, we show that expressing inverted-repeat constructs that generate HaHB4-derived siRNAs without producing the HaHB4 protein bypasses transgenic growth penalties and instead enhances vegetative vigor and reproductive performance. In Arabidopsis, these DCL-dependent siRNA-producing lines exhibited enhanced root growth, increased stem and pith areas, increased cauline branching, and higher seed yield under both optimal and water-limiting conditions. Transcriptomic analysis revealed convergent repression of biotic stress-related genes, accompanied by increased bacterial susceptibility and reduced sensitivity to salicylic acid-mediated growth inhibition, suggesting an altered balance between immunity and growth. Functional characterization of candidate endogenous HD-Zip I targets further showed that athb20 and athb53 mutants recapitulated the increased stem expansion and cauline branching of the RNAi lines, respectively, pointing to endogenous HD-Zip I genes as candidate mediators of these traits. Remarkably, these effects were observed in newly obtained transgenic soybean plants, where expression of HaHB4-derived siRNAs enhanced vegetative vigor under controlled growth conditions. Overall, these findings show that transgene-derived siRNAs act independently of protein function to rewire endogenous regulatory networks, providing a potential strategy to optimize crop architecture and yield.
Gustavo J. Vannay, Joaquín E. García, J. Murguia et al.· bioRxiv· 0 citations
Pentatricopeptide repeat (PPR) proteins are key regulators of the organellar RNA metabolism in plants. However, the functions of mitochondrial PPR proteins belonging to the subclass of P‐type PPR factors containing the SMR domain remain much less understood. Here, we characterize the EMBRYO DEFECTIVE 2217 (EMB2217/At1g79490), an essential PPR‐SMR factor in Arabidopsis thaliana. T‐DNA insertional lines at the AT1G79490 gene‐locus exhibit embryonic arrest at the late heart stage and display defective germination and seedling establishment. Partial complementation using an ABI3 promoter‐driven strategy enables efficient germination and the rescue of homozygous emb2217 plantlets. The pABI3::EMB2217 emb2217 −/− seedlings display severe growth defects due to impaired mitochondrial function, tightly associated with impaired OXPHOS activity. Analyses of mitochondrial RNA profiles reveal that EMB2217 is required for the processing of multiple group II introns that reside in the coding regions of several complex I (CI) subunits, the cox2 subunit of CIV, and the ribosomal rps3 factors. Our data further show that RNA maturation defects induce alternative electron transport and stress‐response pathways, which are associated with developmental defects and modulation of photosynthetic and cellular metabolic processes. Together, we identify EMB2217 as a general mitochondrial splicing factor whose loss compromises OXPHOS biogenesis and function, cellular energy supply, and plant development.
F. Marchetti, Nehuen Balestieri, Evelyn Becerra-Agudelo et al.· Physiologia Plantarum : An I...· 0 citations
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