Analysis of Cytoplasmic Effects and Fine-Mapping of a Genic Male Sterile Line in Rice

<div><p>Cytoplasm has substantial genetic effects on progeny and is important for yield improvement in rice breeding. Studies on the cytoplasmic effects of cytoplasmic male sterility (CMS) show that most types of CMS have negative effects on yield-related traits and that these negative effects vary among CMS. Some types of genic male sterility (GMS), including photo-thermo sensitive male sterility (PTMS), have been widely used in rice breeding, but the cytoplasmic effects of GMS remain unknown. Here, we identified a GMS mutant line, <i>h₂s</i>, which exhibited small, white anthers and failed to produce mature pollen. Unlike CMS, the <i>h₂s</i> had significant positive cytoplasmic effects on the seed set rate, weight per panicle, yield, and general combining ability (GCA) for plant height, seed set rate, weight per panicle, and yield. These effects indicated that <i>h₂s</i> cytoplasm may show promise for the improvement of rice yield. Genetic analysis suggested that the phenotype of <i>h₂s</i> was controlled by a single recessive locus. We mapped <i>h₂s</i> to a 152 kb region on chromosome 6, where 22 candidate genes were predicted. None of the 22 genes had previously been reported to be responsible for the phenotypes of <i>h₂s</i>. Sequencing analysis showed a 12 bp deletion in the sixth exon of <i>Loc_Os06g40550</i> in <i>h₂s</i> in comparison to wild type, suggesting that <i>Loc_Os06g40550</i> is the best candidate gene. These results lay a strong foundation for cloning of the <i>H₂S</i> gene to elucidate the molecular mechanism of male reproduction.</p> </div

<i>h₂s</i> cytoplasmic effects on seed set rate, weight/panicle and yield in comparison with Zhenshan97A (A2), D702A (A3), G46A (A4), K18A (A5) and XieqingzaoA (A6).

<p>The numbers separated by slashes represent data from different years, 2006 (left) and 2008 (right). *and **Significant at 0.05 and 0.01 probability level, respectively.</p

Phenotypic comparison of wild type (WT) and <i>h₂s</i>.

<p>Comparison between WT (left) and <i>h₂s</i> (right) for heading plant (A), headed panicle (B, C), flower (D) and pollen of WT (E) and anther of <i>h₂s</i> (F).</p

Candidate genes in the 154 kb region on chromosome 6 where <i>h₂s</i> locus was fine mapped.

*<p>expressed in inflorescence.</p

Sequencing analysis of candidate gene <i>Loc_Os06g40550.</i>

<p>(A) Schematic structure of gene <i>Loc_Os06g40550</i>, 12 bp deletion was detected at the predicted sixth exon. White and grey boxes for UTR regions and exons, respectively. The gray lines for introns, and the black dash box for ABC transporter domain region. (B) RT-PCR examination of 12 deletion in <i>Loc_Os06g40550</i> RNA. The deletion was detected in the RNA of heterozygous and homozygous plants.</p

Linkage mapping of the <i>h₂s</i> gene.

<p>(A) Preliminary mapping results using a population of <b><i>h₂s</i></b>/Zhensan97B and (B) fine mapping results using a population of <b><i>h₂s</i></b>/Nipponbare. Genetic distance between a marker and the <i>h₂s</i> gene is given on the left in centimorgans (cM).D.</p

DAPI staining analysis for the meiosis of microspore mother cells and mitosis of young microspores between the wild type (WT) and <i>h₂s</i>.

<p>(A–I) and (K–S) for WT, (B–J) and (L–T) for <i>h₂s</i>; (A) and (B) Pachytene, (C) and (D) diakinesis, (E) and (F) metaphase I, (G) and (H) anaphase I, (I) and (J) telophase I, (K) and (L) prophase II, (M) and (N) metaphase II, (O) and (P) tetrad, (Q) and (R) young microspore stage, and (S) and (T) vacuolated pollen stage. No difference in the process of meiosis was observed between WT and <i>h2s</i>. Bars = 10 µm.</p

Section analysis between the wild type (WT) and <i>h₂s.</i>

<p>(A–D) for WT, (E–G) for <i>h2s</i>. (A) and (E) Meiosis, (B) and (F) post-meiotic stage, (C) and (G) young microspore stage. The young microspores in <i>h2s</i> exhibited defects at the post-meiotic stage (D) and vacuolated pollen stage (H). However, no microspore was observed at the vacuolated pollen stage. E: epidermis; En: endothecium; T: tapetum; Ms: microsporocyte; Msp: microspore; Tds: tetrad; bars = 15 µm.</p

GCA effects on seed set rate, weight per panicle and yield among cytoplasms of <i>h₂s</i> (A1), Zhenshan97A (A2), D702A (A3), G46A (A4), K18A (A5) and XieqingzaoA (A6).

<p>The numbers separated by slashes represent the data from different years, 2006 (left) and 2008 (right). Values followed by the same letter in a column within a year are not significantly different at α = 0.05.</p

Enhanced Charge Injection and Collection of Niobium-Doped TiO₂/Gradient Tungsten-Doped BiVO₄ Nanowires for Efficient Solar Water Splitting

Extensively investigated BiVO₄ photoanode for solar water splitting suffers from low product of light absorption and charge separation efficiency (η_abs × η_sep) due to the lack of high surface area supporting materials as a charge collector. Such a host|guest heterostructure is not only effective but also attractive, but it is too complicated to understand the original process of η_sep. Here, a host–guest heterostructure of Nb-doped TiO₂ nanowires supporting BiVO₄ nanoparticles is fabricated to investigate its visible-light charge injection efficiency (η_inj) and charge collection efficiency (η_col). With the aid of gradient W doping in BiVO₄ guest, the Nb-doped TiO₂|gradient W-doped BiVO₄ (N:T|g-W:B) produces η_inj = 82% and η_col = 95% to yield a very high value for η_abs × η_sep of 55.3% at 0.6 V_RHE, which is one of the highest values among these nanostructure-host|BiVO₄-geust photoanodes. By being further coated with Co–Pi, the photoanode simultaneously achieves a high value of η_trans for efficient solar water splitting