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tRNA selectivity during ribosome-associated quality control regulates the critical sterility-inducing temperature in two-line hybrid rice
Wednesday, 2025/02/19 | 08:29:28
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Can Zhou, Chunyan Liu, Bin Yan, Jing Sun, Shengdong Li, Ji Li, Jia Wang, Xiahe Huang, Wei Yan,
PNAS, February 6, 2025 122 (6) e2417526122; https://doi.org/10.1073/pnas.2417526122 SignificanceIn two-line hybrid rice, the critical sterility-inducing temperature (CSIT) acts as a key threshold for thermo-sensitive genic male sterile (TGMS) lines. However, reports on regulatory mechanisms controlling CSIT are limited. Here, we demonstrated that an amino acid substitution (T552I) in the rice Rqc2 (ribosome-associated quality control 2) protein increases CSIT of TGMS lines containing thermo-sensitive genic male sterility 5 (tms5). T552I mutation decelerates the C-terminal alanine and threonine modification (CATylation) rate of nascent chains and alters tRNA selectivity during ribosome-associated quality control (RQC), thereby increasing mature tRNA-Ser/Ile levels and raising the CSIT of tms5 lines. Our work links tRNA selection during CATylation to CSIT in rice, deepening our understanding of the regulatory network controlling CSIT in TGMS lines containing tms5. AbstractThe two-line hybrid rice system, a cutting-edge hybrid rice breeding technology, has greatly boosted global food security. In thermo-sensitive genic male sterile (TGMS) lines, the critical sterility-inducing temperature (CSIT; the temperature at which TGMS lines change from male fertile to complete male sterile) acts as a key threshold. We recently uncovered that thermo-sensitive genic male sterility 5 (tms5), a sterile locus presenting in over 95% of TGMS lines, leads to the overaccumulation of 2′,3′-cyclic phosphate (cP)-ΔCCA-tRNAs and a deficiency of mature tRNAs, which underlies the molecular mechanism of tms5-mediated TGMS. However, there are a few reports on the regulatory mechanism controlling CSIT. Here, we identified a suppressor of tms5, an amino acid substitution (T552I) in the rice Rqc2 (ribosome-associated quality control 2), increases the CSIT in tms5 lines through its C-terminal alanine and threonine modification (CATylation) activity. This substitution alters tRNA selectivity, leading to the recruitment of different tRNAs to the A-site of ribosome and CATylation rate by OsRqc2 during ribosome-associated quality control (RQC), a process that rescues stalled ribosomes and degrades abnormal nascent chains during translational elongation. Further, the mutation restores the levels of mature tRNA-Ser/Ile to increase the CSIT of tms5 lines. Our findings reveal the origin of overaccumulated cP-ΔCCA-tRNAs in tms5 lines, further deepening our understanding of the regulatory network in governing CSIT of TGMS lines containing tms5.
See https://www.pnas.org/doi/10.1073/pnas.2417526122
Figure 1: T552I, an evolutionarily differentiated residue in OsRqc2 among bacteria, archaea, and eukaryotes, increases the CSIT in tms5. (A) Sequence conservation of part of the NFACT-N domain and the CC2 domain among OsRqc2 homologs in bacteria, archaea, and eukaryotes (plants, animals, and fungi) (see Dataset S1 for species abbreviations). The secondary structure predicted by JNETHMM is shown below the alignment (α helices in red, β strands in green). Conserved residues are highlighted with the following colors: red, basic; blue, hydrophobic; green, small polar; purple, acidic. All of the Gly (orange) and Pro (yellow) residues are indicated. The conserved residue in OsRqc2 (D104) is represented by a black asterisk, and the residue that differentiated during evolution (T552) is represented by a red asterisk. (B) Plant morphology of Zhu1, Zhu1S, tms5 osrqc2-1, two independent wild-type OsRqc2 complementation lines (OsRqc2-C1 and OsRqc2-C2), and OsRqc2 complementation lines with two functional mutations (D104A-1, D104A-2, T552L-1, and T552L-2) in the tms5 osrqc2-1 background grown in the field (daily average temperature ~27 °C). (White Scale bar, 20 cm.) White dotted lines were employed to delineate and present the different photographs; same hereafter. (C) Pollen fertility of these lines in (B) grown at 22 °C, 25 °C, and 30 °C. (Black Scale bar, 100 μm.) (D) Statistical analysis of pollen fertility in (C). Error bars indicate SD (n = 10 replicates). Different letters indicate significant differences, as determined by one-way ANOVA with Tukey’s multiple comparisons test at P < 0.05.
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