Development of introgression lines and mapping of qGW2, a novel QTL that confers grain width, in rice (Oryza sativa L.).

Rice grain size is a key determinant of both grain yield and quality. Identification of favorable alleles for use in rice breeding may help to meet the demand for increased yield. In this study, we developed a set of 210 introgression lines (ILs) by using indica variety Huanghuazhan as the donor parent and erect-panicle japonica rice variety Wuyujing3R as the recurrent parent. A total of 133 ILs were selected for high-throughput sequencing. Using specific-locus amplified fragment (SLAF) sequencing technology, 10,103 high-quality SLAF labels evenly distributed on 12 chromosomes were obtained and selected for subsequent analysis. Using a high-density map, quantitative trait locus (QTL) mapping of grain size-related traits was performed, and a total of 38 QTLs were obtained in two environments. Furthermore, qGW2, a novel QTL that controls grain width on chromosome 2, was validated and delimited to a region of 309 kb via substitution mapping. These findings provide new genetic material and a basis for future fine mapping and cloning of favorable QTLs. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-024-01453-0.

Mapping of Rf20(t), a minor fertility restorer gene for rice wild abortive cytoplasmic male sterility in the maintainer line 'Zhenshan97B'.

Three-line hybrid rice has primarily been developed on wild abortive (WA)-type cytoplasmic male sterility (CMS) and has helped increase the yield of rice globally. The development of WA-type CMS lines and hybrids was expedited through the identification and mapping of the fertility restorer gene (Rf) in maintainers. This study observed fertile plants in WA-TianfengA/Zhenshan97B//TianfengB population, indicating that the maintainer line 'Zhenshan97B' should carry Rfs for WA-type CMS. Several advanced backcross populations were generated with the genetic background of the 'WA-TianfengA,' and the pollen fertility levels of the backcrossed individuals in BC3F1, BC4F1 and BC4F2 populations are governed by a new gene, Rf20(t), from 'Zhenshan97B.' Employing bulk segregant analysis of fertile and sterile pools from the BC4F1 population, Rf20(t) was genetically mapped to a candidate region on chromosome 10. Subsequently, Rf20(t) was located between RM24883 and RM24919 through recombination analysis of molecular markers using the BC4F2 population. Implementing a substitution mapping strategy, Rf20(t) was ultimately mapped to a 245-kb region between the molecular markers STS10-122 and STS10-126 and obtained the most likely candidate gene LOC_Os10g02650, which is predicted to encode pentatricopeptide repeat-containing (PPR) protein. These results enhance our understanding of the fertility restoration of WA-type CMS lines, facilitating the development of high-quality pairs of WA-type CMS and maintainer lines.

The Effects of Rf4 and the Genetic Mechanism Behind Fertility Restoration of Wild Abortive Cytoplasmic Male Sterility (WA-CMS) in Japonica Rice (Oryza sativa ssp. Japonica).

Wild abortive-type cytoplasmic male sterility (WA-type CMS) has been exclusively used in hybrid seed production in indica rice cultivars, and fertility restoration in WA-type CMS is controlled by two major restorer genes, Rf3 and Rf4, through a sporophytic mechanism. However, the genetic mechanism underlying fertility restoration in WA-type CMS in japonica cultivars is poorly understood. In the present study, C418, a leading Chinsurah Boro II- (BT)-type japonica restorer line, showed partial restoration ability in WA-type japonica CMS lines. The 1:1 segregation ratio of partially fertile to sterile plants in a three-cross F1 population indicated that fertility restoration is controlled by one dominant gene. Gene mapping and sequencing results revealed that the target gene should be Rf4. The Rf4 gene restores fertility through a sporophytic mechanism, but the Rf4 pollen grains show a preferential fertilization in the testcross F1 plants. Furthermore, Rf4 was confirmed to have only a minor effect on fertility restoration in WA-type japonica CMS lines, and Rf gene dosage effects influenced the fertility restoration of WA-type CMS in japonica rice. The results of our study not only provide valuable insights into the complex genetic mechanisms underlying fertility restoration of WA-type CMS but will also facilitate the efficient utilization of WA-type CMS in japonica rice lines.

Precise genetic mapping of Rf18(t), a new fertility restorer gene from 'Nipponbare' for wild abortive cytoplasmic male sterility in rice (Oryza sativa L.).

KEY MESSAGE: We mapped Rf18(t), a Restorer-of-fertility gene for wild abortive cytoplasmic male sterility from the japonica maintainer 'Nipponbare', to chromosome 1. The best candidate gene, LOC_Os01g71320, is predicted to encode hexokinase. Three-line hybrid rice obtained through cytoplasmic male sterility (CMS) has helped increase the yield of rice globally, and the wild abortive (WA)-type cytoplasm from wild rice (Oryza rufipogon Griff.) is used widely in three-line indica hybrids. The identification and mapping of the Restorer-of-fertility (Rf) genes in maintainer lines aided in uncovering the genetic basis of fertility restoration of WA-type CMS and the development of WA-type hybrids. In this study, we identified a new Rf gene, Rf18(t), for WA-type CMS from the japonica maintainer line 'Nipponbare' using a chromosome segment substitution line population derived from a cross between the indica line 9311 and 'Nipponbare.' Using a substitution mapping strategy, Rf18(t) was delimited to a 48-kb chromosomal region flanked by molecular marker loci ID01M28791 and ID01M28845 on chromosome 1. By comparative sequence analyses, we propose that LOC_Os01g71320 is the most likely candidate gene for Rf18(t), and it is predicted to encode hexokinase. Furthermore, Rf18(t) was found to function in fertility restoration probably by a posttranscriptional mechanism and its function is dependent on the genetic background of 9311. These results broaden our knowledge on the mechanism of fertility restoration of WA-type CMS lines and will facilitate the development of WA-type rice hybrids.

Transcriptome profiling reveals that foliar water uptake occurs with C3 and crassulacean acid metabolism facultative photosynthesis in Tamarix ramosissima under extreme drought.

Tamarix ramosissima is a typical desert plant species that is widely distributed in the desert areas of Northwest China. It plays a significant role in sand fixation and soil water conservation. In particular, how it uses water to survive in the desert plays an important role in plant growth and ecosystem function. Previous studies have revealed that T. ramosissima can alleviate drought by absorbing water from its leaves under extreme drought conditions. To date, there is no clear molecular regulation mechanism to explain foliar water uptake (FWU). In the present study, we correlated diurnal meteorological data, sap flow and photosynthetic parameters to determine the physical and biological characteristics of FWU. Our results suggested that the lesser the groundwater, the easier it is for T. ramosissima to absorb water via the leaves. Gene ontology annotation and Kyoto Encyclopaedia of Genes and Genomes pathway analysis of the transcriptome profile of plants subjected to high humidity suggested that FWU was highly correlated to carbohydrate metabolism, energy transfer, pyruvate metabolism, hormone signal transduction and plant-pathogen interaction. Interestingly, as a C3 plant, genes such as PEPC, PPDK, MDH and RuBP, which are involved in crassulacean acid metabolism (CAM) photosynthesis, were highly upregulated and accompanied by FWU. Therefore, we proposed that in the case of sufficient water supply, C3 photosynthesis is used in T. ramosissima, whereas in cases of extreme drought, starch is degraded to provide CO2 for CAM photosynthesis to make full use of the water obtained via FWU and the water that was transported or stored to assimilating branches and stems. This study may provide not only an important theoretical foundation for FWU and conversion from C3 plants to CAM plants but also for engineering improved photosynthesis in high-yield drought-tolerant plants and mitigation of climate change-driven drought.

The effects of Rf5 and Rf6 on fertility restoration in Honglian-type cytoplasmic male sterile (CMS) lines of japonica rice (Oryza sativa L. ssp. japonica).

Honglian (HL)-type cytoplasmic male sterility (CMS) has only been used in the development of three-line indica rice hybrids, and the fertility of HL-type indica CMS lines can be restored by two non-allelic fertility-restorer (Rf) genes, Rf5 and Rf6. For the development of HL-type japonica hybrid combinations, it is therefore necessary to determine whether Rf5 and Rf6 can restore the fertility of HL-type japonica CMS lines. Here, we genetically characterized HL-type japonica CMS lines and the ability of Rf5 and Rf6 to restore fertility for breeding HL-type japonica hybrids. I2-KI pollen staining revealed that HL-type japonica CMS lines and their derived testcross F1 hybrids had stained abortive pollen grains, unlike HL-type indica CMS lines. Crossing experiments showed that Rf5 and Rf6 partially restored the fertility of HL-type japonica CMS lines, and Rf6 showed higher restorability than Rf5. Furthermore, we found that there were additive and dosage effects of Rf5 and Rf6 with respect to fertility restoration in HL-type japonica CMS lines. These results give critical insight into the breeding of HL-type japonica CMS lines and restorers, which will be helpful for the development of commercial HL-type japonica hybrids. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-021-01256-7.

Overexpression of the Transcription Factor Gene OsSTAP1 Increases Salt Tolerance in Rice.

BACKGROUND: High soil salinity can cause significant losses in rice productivity worldwide, mainly because salt inhibits plant growth and reduces grain yield. To cope with environmental changes, plants have evolved several adaptive mechanisms that involve the regulation of many stress-responsive genes. RESULTS: In this study, we identified OsSTAP1, which encodes an AP2/ERF-type transcription factor, was rapidly induced by ABA, ACC, salt, cold, and PEG treatments. OsSTAP1 is localized to the nucleus and acts as a transcriptional activator in plant cells. Compared with wild type, transgenic lines overexpressing OsSTAP1 exhibited increased tolerance to salt stress with higher SOD, POD, and CAT activities, and lower Na+/K+ ratios in the shoots. In addition, many other stress-responsive genes, including other ERF- and peroxidase-encoding genes, were upregulated in the OsSTAP1-overexpression lines. CONCLUSION: This study suggests that OsSTAP1 functions as an AP2/ERF transcriptional activator, and plays a positive role in salt tolerance by decreasing the Na+/K+ ratio and maintaining cellular redox homeostasis.

[Improvement of the bilingual teaching of genetics using classic papers].

More and more colleges have recognized the importance of bilingual teaching in improvement students' capability to integrate the specialized knowledge with the foreign language. Bilingual teaching courses have been designed to enhance the innovation of high education and improve the culture quality of students. Genetics is one of the most important courses for undergraduate students majored in the region of life sciences. However, in the case of genetics, the advisable model to carry out bilingual teaching and the matter of great concern are ambiguous and need evidence accumulated by more teaching experiments. The classic papers in genetics are valuable resources to the bilingual teaching of genetics. This paper analyzed the role of classic papers in the bilingual teaching of genetics and discussed the methods for improving the bilingual teaching of genetics.

[A preliminary exploration into medical genetics teaching to international students].

Medical education to international students has become an important part of higher education in China. Medical genetics is an essential and required course for international medical students. However, the internationalization of higher education in China has challenged the traditional teaching style of medical genetics. In this article, we discussed current situation and challenges in medical genetics teaching to international students, summarized special features and problems we encountered in teaching Indian students, and proposed some practical strategies to address these challenges and to improve the teaching.

[Molecular mapping of two semidwarf genes in an indica rice variety Aitaiyin3 (Oryza sativa L.)].

The rice dwarf variety Aitaiyin3 is derived from a semidwarf cultivar Taiyin1. Genetic analysis indicated that the dwarf phenotype in Aitaiyin3 is involved in two recessive loci. Using bulk analysis with SSR markers, the two loci were located on the chromosome 1 and chromosome 4, respectively. Moreover, the allelism test showed that the locus on the chromosome 1 is allelic to the semidwarf gene sd1, while the other one is a new locus, here was named as sdt2. Further molecular mapping showed that sd1 was linked with SSR markers in the order of RM297-RM302-RM212-OSR3-sd1 with genetic distances of 4.7 cM, 0 cM, 0.8 cM and 0 cM, respectively. The linkage relationship of sdt2 with five SSR markers was SSR332-RM1305-sdt2-RM5633-RM307-RM401 with genetic distances of 11.6 cM, 3.8 cM, 0.4 cM, 0 cM and 0.4 cM, respectively.