Thermo-sensitive Genic Male Sterility Research Articles

Photosynthesis and Hill Reaction - a Physiological Inquiry into a Thermosensitive Genic Male Sterile (TGMS) Rice Used in Two Line Breeding

An investigation was carried out to understand the physiological mechanisms of male sterility in rice. The critical sterility temperature and critical stage of thermosensitivity of the selected TGMS (Thermosensitive Genie Male Sterile) line, TS 29 was studied using a Phytotron. Variations in the physiological traits were analyzed at Stage VII of panicle development (Filling phase of pollen, floret and panicle reach full length and colour turns to green). High significant reductions in photosynthetic rate, transpiration rate, hill reaction, sugars and carbohydrate contents were recorded. The high temperature induced male sterility in TGMS line was associated with accumulation of starch and higher diffusive resistance. However a reverse of all the above responses was found in the TS 29 grown under fertility inducing low temperature and in the variety CO 46. The results revealed that some physiological traits play an important role by acting as signals or messengers in response to temperature leading to pollen abortion.

Fine mapping and candidate gene analysis of the novel thermo-sensitive genic male sterility tms9-1 gene in rice

Fine mapping of the novel thermo-sensitive genic male sterility locus tms9 - 1 in the traditional TGMS line HengnongS-1 revealed that the MALE STERILITY1 homolog OsMS1 is the candidate gene. Photoperiod-thermo-sensitive genic male sterility (P/TGMS) has been widely used in the two-line hybrid rice breeding system. HengnongS-1 is one of the oldest TGMS lines and is often used in indica two-line breeding programs in China. In this study, our genetic analysis showed that the TGMS gene in HengnongS-1 was controlled by a single recessive gene that was non-allelic with the other TGMS loci identified, including C815S, Zhu1S and Y58S. Using SSR markers and bulked segregant analysis, we located the TGMS locus on chromosome 9 and named the gene tms9-1. Fine mapping further narrowed the tms9-1 loci to a 162kb interval between two dCAPS markers. Sequence analysis revealed that a T to C substitution results in an amino acid change in the tms9-1 candidate gene (Os09g27620) in HengnongS-1 as compared to Minghui63. Sequencing of other rice accessions, including six P/TGMS lines, seven indica varieties and nine japonica varieties, showed that this SNP was exclusive to HengnongS-1. With multiple sequence alignment and expression pattern analyses, the rice MALE STERILITY1 homolog OsMS1 gene was identified as the candidate gene for tms9-1. Therefore, our study identified a novel TGMS locus and will facilitate the functional identification of the tms9-1 gene. Moreover, the markers linked to the tms9-1 gene will provide useful tools for the development of new TGMS lines by marker-assisted selection in two-line hybrid rice breeding programs.

Introgression of Gene for Non-Pollen Type Thermo-Sensitive Genic Male Sterility to Thai Rice Cultivars

For the two-line hybrid rice system, pollen sterility is regulated by recessive gene that responds to temperature. The recessive gene controlling thermo-sensitive genetic male sterility (TGMS) is expressed when the plants are grown in conditions with higher or lower critical temperatures. To transfer tgms gene(s) controlling TGMS to Thai rice cultivars by backcross breeding method, a male sterile line was used as a donor parent while Thai rice cultivars ChaiNat 1, PathumThani 1, and SuphanBuri 1 were used as recurrent parents. The BC2F2 lines were developed from backcrossing and selfing. Moreover, the simple sequence repeat (SSR) markers were developed for identifying tgms gene and the linked marker was used for assisting selection in backcrossing. The identification lines were confirmed by pollen observation. The results showed the success of introgression of the tgms gene into Thai rice cultivars. These lines will be tested for combining ability and used as female parent in hybrid rice production in Thailand.

Sterility mechanism in different TGMS and CMS lines of rice

Thermosensitive genic male sterility (TGMS) is a new genetic tool used in developing commercial F 1 rice hybrids. This study investigated the stage at which sterility occurs during anther development in TGMS lines. For critical examination, panicles were collected from TGMS lines TS16, TS18, TS29, and cytoplasmic male sterile (CMS) lines IR58025A and IR62829A. In the TGMS lines, the developmental stages of young panicles were examined at stages IV, V, and VI in September 1998 and May 1999 for the expression of fertility and sterility, respectively. Anthers were taken out from the spikelet and fixed in 70% alcohol for 1 h. These were then passed through a series of solutions containing alcohol and methyl salicylate in the proportion of 4:1, 3:2, 2:3, and 1:4, and finally in methyl salicylate for 15 min in each solution with two changes in the last step. Cleared anthers were mounted in methyl salicylate in a cavity microslide and examined using a Namarski differential interference contrast in a bright field microscope for optimal viewing and microphotography.

Elongation of the uppermost internode for Shuangdi Pei eS, TGMS rice with eui gene

Shuangdi Pei eS, a thermo-sensitive genic male sterile (TGMS) rice line with eui gene is derived from TGMS rice line Shuangdi S by irradiation with 350 Gy60Co γ-ray. To elucidate the uppermost internode elongation of TGMS line with eui gene, Shuangdi Pei eS and its original TGMS line Shuangdi S were used to study the effects of temperature on panicle exsertion. At 25°C, the uppermost internode of Shuangdi Pei eS had the quickest elongation from the 4th day before flowering to 0 day (flowering), being 2.1-fold as that of Shuangdi S, whereas it elongated slowly during the 12th day to the 4th day before flowering and the 1st to the 3rd day after flowering. The uppermost internode of Shuangdi Pei eS exserted from the flag leaf sheath at 23, 25 and 27°C, respectively, and the length of elongated uppermost internode increased with the decreasing temperatures. At 30°C, though the panicles of Shuangdi Pei eS were still enclosed in the leaf sheath, the degree of panicle enclosure was significantly lower compared with Shuangdi S. Cytological studies on Shuangdi Pei eS which showed that the uppermost internode elongation was attributed to the increase of cell number and cell elongation, and the latter was more significant. Moreover, the numbers of outermost and innermost parenchyma cells and the cell length of the uppermost internode reduced with the increasing temperatures. Key words: Rice (Oryza sativa L.), thermo-sensitive genic male sterility (TGMS), elongated uppermost internode gene (eui), panicle exsertion, temperature.

Genetics of the thermosensitive genic male sterility trait in rice

UPRI 95-140 (P1), the thermosensitive genic male sterile (TGMS) line of low temperature fertility transformation type, was analyzed for its inheritance and transformation behavior. Parents, F1, F2, and six test crosses between TGMS (female parent) and UPRI 95-141 (P2), UPRI 95-165 (P3), UPRI 95-124 (P4), UPRI 95-117 (P5), and IR36 (P6) were screened in the field during the main season.

Identifying rice genotypes with the TGMS trait suitable for north India

The discovery of the environment-sensitive genic male sterility (EGMS) system laid the foundation for replacing the three-line system with the simpler and more efficient two-line system for hybrid rice seed production. EGMS includes photoperiod-sensitive genic male sterility (PGMS) and thermosensitive genic male sterility (TGMS) systems. The required day length differences do not occur in our rice seasons for PGMS seed production. Therefore, we attempted to develop suitable TGMS lines in India.

Male sterility and fertility behavior of suspected thermosensitive genic male sterile (TGMS) lines

The male sterility-fertility response in thermosensitive genic male sterile (TGMS) lines was studied to identify their adaptability to different temperature regimes. Twenty suspected TGMS lines available at the Paddy Breeding Station, Coimbatore, were used for the study. The plants of these lines, which were completely male sterile during summer 1995, were tagged and observed for their male sterility-fertility behavior in the ratooned tillers during winter 1995 and summer 1996 by staining pollen grains with I-KI. Panicle development stages, from the formation of pollen mother cells to the late uninucleate stage of pollen grains, were considered as sensitive to temperature. These stages occurred 9-19 d prior to heading (or 9-17 d after panicle initiation). Therefore, the critical temperature at which plants showed variation in pollen sterility and fertility was calculated by considering the average daily temperature and average maximum temperature prevalent during 9-19 d prior to heading.

Developing thermo-sensitive genic male sterile lines in rice

The three-line method (A/B/R) of heterosis breeding is cumbersome and warrants development of alternate approaches to exploit hybrid vigor commercially in rice. Two-line breeding is one such possibility that emerged following the chance discovery of photoperiod-sensitive genic male sterile (PGMS) lines and thermosensitive genic male sterile (TGMS) lines in China.

Field evaluation of thermosensitive genic male sterile lines

The use of thermosensitive genic male sterility (TGMS) is well recognized in two-line heterosis breeding. The use of the TGMS system has several advantages over the cytoplasmic genic male sterility system, such as (1) its simple and efficient seed production system, and (2) its greater scope for enhancing heterosis because any genotype can be used as a male parent. To develop hybrids using the TGMS system, it is necessary to identify or develop lines that show a desirable transformation from fertility to sterility and vice versa.

Uncovering Small RNA-Mediated Responses to Cold Stress in a Wheat Thermosensitive Genic Male-Sterile Line by Deep Sequencing

The male sterility of thermosensitive genic male sterile (TGMS) lines of wheat (Triticum aestivum) is strictly controlled by temperature. The early phase of anther development is especially susceptible to cold stress. MicroRNAs (miRNAs) play an important role in plant development and in responses to environmental stress. In this study, deep sequencing of small RNA (smRNA) libraries obtained from spike tissues of the TGMS line under cold and control conditions identified a total of 78 unique miRNA sequences from 30 families and trans-acting small interfering RNAs (tasiRNAs) derived from two TAS3 genes. To identify smRNA targets in the wheat TGMS line, we applied the degradome sequencing method, which globally and directly identifies the remnants of smRNA-directed target cleavage. We identified 26 targets of 16 miRNA families and three targets of tasiRNAs. Comparing smRNA sequencing data sets and TaqMan quantitative polymerase chain reaction results, we identified six miRNAs and one tasiRNA (tasiRNA-ARF [for Auxin-Responsive Factor]) as cold stress-responsive smRNAs in spike tissues of the TGMS line. We also determined the expression profiles of target genes that encode transcription factors in response to cold stress. Interestingly, the expression of cold stress-responsive smRNAs integrated in the auxin-signaling pathway and their target genes was largely noncorrelated. We investigated the tissue-specific expression of smRNAs using a tissue microarray approach. Our data indicated that miR167 and tasiRNA-ARF play roles in regulating the auxin-signaling pathway and possibly in the developmental response to cold stress. These data provide evidence that smRNA regulatory pathways are linked with male sterility in the TGMS line during cold stress.

Exploiting heterosis using TGMS lines in intra- and intersubspecific hybridization

The performance of various thermo- sensitive genic male sterile (TGMS) lines was assessed in order to use them in two-line intra- and intersubspecific hybridization with wide compatibility lines. Some 26 lines comprising TGMS lines, indica accessions, and japonica with wide compatibility (WC) gene(s) were used to make 65 hybrids: 31 were indica/indica and 34 were indica/japonica (WC). Standard heterosis was recorded up to 58%. Seed yield (g plant -1 ) ranged from 2.3 to 31.3. The number of heterotic combinations was higher in intersubspecific cross combinations. Spikelet fertility ranged from 2.7 to 88.4% in intersubspecific crosses and from 3.6 to 96.0% in intrasubspecific crosses. The WC lines were not univer- sally compatible in all combinations.

Characterizing thermosensitive genic male sterile lines of rice

The cytoplasmic male sterility (CMS) system is widely used to develop rice hybrids. Although effective, this system is quite cumbersome to practice. Certain genic male sterile lines that revert to fertility under specific temperature are called thermosensitive genic male sterile (TGMS) lines. Deployment of the TGMS system to develop two-line hybrids has several advantages over the conventional CMS system, as it requires neither maintainers for seed multiplication nor restorers for producing hybrids. In addition, two-line hybrids may not suffer from possible negative effects of the sterility-inducing cytoplasm.

Exploiting the in vitro ovary culture technique to breed rice hybrids

The thermosensitive genic male sterility (TGMS) system has a high potential to develop two-line hybrids, which are more economical for seed production. The ovary culture technique can also help to improve or develop new lines for several economic traits. We therefore cultured unpollinated ovaries from plants of five crosses involving TGMS UPRI 95-140 (P1), the good ideotype UPRI 95-117 (P2), and main- tainers UPRI 95-139 (P3) and UPRI 95-130 (P4). Quality rices-Basmati 385 (P5), Haryana Basmati 1 (P6), and UPRI 95-145 (P7)-were also cultured.

Photoperiod- and thermo-sensitive genic male sterility in rice are caused by a point mutation in a novel noncoding RNA that produces a small RNA

Photoperiod- and thermo-sensitive genic male sterility (PGMS and TGMS) are the core components for hybrid breeding in crops. Hybrid rice based on the two-line system using PGMS and TGMS lines has been successfully developed and applied widely in agriculture. However, the molecular mechanism underlying the control of PGMS and TGMS remains obscure. In this study, we mapped and cloned a major locus, p/tms12-1 (photo- or thermo-sensitive genic male sterility locus on chromosome 12), which confers PGMS in the japonica rice line Nongken 58S (NK58S) and TGMS in the indica rice line Peiai 64S (PA64S, derived from NK58S). A 2.4-kb DNA fragment containing the wild-type allele P/TMS12-1 was able to restore the pollen fertility of NK58S and PA64S plants in genetic complementation. P/TMS12-1 encodes a unique noncoding RNA, which produces a 21-nucleotide small RNA that we named osa-smR5864w. A substitution of C-to-G in p/tms12-1, the only polymorphism relative to P/TMS12-1, is present in the mutant small RNA, namely osa-smR5864m. Furthermore, overexpression of a 375-bp sequence of P/TMS12-1 in transgenic NK58S and PA64S plants also produced osa-smR5864w and restored pollen fertility. The small RNA was expressed preferentially in young panicles, but its expression was not markedly affected by different day lengths or temperatures. Our results reveal that the point mutation in p/tms12-1, which probably leads to a loss-of-function for osa-smR5864m, constitutes a common cause for PGMS and TGMS in the japonica and indica lines, respectively. Our findings thus suggest that this noncoding small RNA gene is an important regulator of male development controlled by cross-talk between the genetic networks and environmental conditions.

Development of specific simple sequence repeat (SSR) markers for non-pollen type thermo-sensitive genic male sterile gene in rice (Oryza sativa L.)

A key factor of two-line hybrid rice production is the development of thermo-sensitive genic male sterility (TGMS) lines. In this study, a TGMS line showing non-pollen type thermo-sensitive genic male sterility was used. Crossing between TGMS line (female parent) and normal pollen varieties; CNT1 and PTT1 (male parent) were performed and F 1 and F 2 populations were develop for each crosses. The phenotypic segregation ratio, 3:1 (fertile: sterile pollens) observed in F 2 populations of TGMS/CNT1 and TGMS/PTT1 crosses confirmed that the non-pollen type thermo-sensitive genic male sterility is controlled by a single recessive gene. The bulk segregant analysis (BSA) using simple sequence repeat (SSR) markers were deployed to identify the location and genetic effect of this gene. We have generated new set of SSR markers to identify progenies carrying TGMS gene in a cross TGMS/PTT1. The TGMS gene was located on chromosome 2 with 0.0 cM distance from T2 marker. This TGMS gene was located in the same region of previous identified tmsX gene. It might be the same allele of this gene of 2 different lines. This marker could be used for marker assisted backcrossing to transfer TGMS gene for developing female parent in two line hybrid rice system. Key words: Hybrid rice, thermo-sensitive genic male-sterile, non-pollen type, molecular marker, marker assisted backcrossing.

Development and Application of a Computer-aided Selection System for Thermo-sensitive Genic Male Sterile Rice Multiplying Site

Great success has been achieved in the utilization of two-line hybrid rice in China.Nevertheless,the seed production of two-line hybrid rice is still a key technology that limited the extension of two-line hybrid rice on large scale.Seed multiplication of the thermo-sensitive genic male sterile (TGMS) rice,which with a narrow range of temperature for fertility restoration,is hard to be success by using the most common multiplying technologies currently.In order to improve the yield stability and security in TGMS rice multiplication,we developed a practical computer selection system for choosing an optimal multiplying site.This system using the java language was able to select suitable multiplying sites with optimal ecological factors which meet the requirement of the fertility sensitive stage (FSS) and heading-flowering stage (HFS) for TGMS rice multiplication.By using this computer-aided selection system,24,29,20,21,and 22 ecological areas were selected,which were superior to the most common seed producing area,Sanya of Hainan province,where the suitable probabilities of FSS and HFS are 35.0%,42.5%,55.0%,65.0%,and 75.0% for the TGMS with the critical temperature of 22.0℃,22.5℃,23.0℃,23.5℃,and 24.0℃,respectively,while the suitable probability of the optimal multiplying site selected by the computer-aided selection system were 83%,93%,100%,100%,and 100% in both FSS and HFS for TGMS with different critical temperature,respectively,showing much higher values than those in Sanya,Hainan Province.In 2010,we tried to produce the seed of C815S,a TGMS rice with the critical temperature of 22.0℃ in Baoshan,Yunnan Province selected by the computer-aided selection system.The grain yield reached 8 437.5 kg ha-1,and created the highest yield record of seed multiplication of the TGMS rice.These results suggested that the problems of unstable yield and low security for the TGMS rice seed multiplication should be solved by this computer aided selection system,and we believe the optimal multiplying site selected by the computer-aided selection system will provide a useful technical support for healthy and sustainable development in the two-line hybrid rice.

Thoughts and Practice on Some Problems about Research and Application of Two-Line Hybrid Rice

The main problems about research and application of two-line hybrid rice were reviewed, including the confusing nomenclature and male sterile lines classification, the unclear characteristics of photoperiod and temperature responses and the unsuitable site selection for male sterile line and hybrid rice seed production. In order to efficiently and accurately use dual-purpose genic male sterile lines, four types, including PTGMS (photo-thermo-sensitive genic male sterile rice), TGMS (thermo-sensitive genic male sterile rice), reverse PTGMS and reverse TGMS, were proposed. A new idea for explaining the mechanism of sterility in dual-purpose hybrid rice was proposed. The transition from sterile to fertile was involved in the cooperative regulation of major-effect sterile genes and photoperiod and/or temperature sensitive ones. The minor-effect genes with accumulative effect on sterility were important factors that affected the critical temperature of sterility transfer. In order to make better use of dual-purpose lines, the characterization of responses to photoperiod and temperature of PTGMS should be made and the identification method for the characterization of photoperiod and temperature responses of PTGMS should also be put forward. The optimal ecological site for seed production could be determined according to the historical climate data and the requirements for the meteorological conditions during the different periods of seed production.

Effect of Temperature on Uppermost Internode Elongation of Thermosensitive-genic Male Sterility Rice with Elongated Upper-most Internode Gene

Effect of Temperature on Uppermost Internode Elongation of Thermosensitive-genic Male Sterility Rice with Elongated Upper-most Internode Gene

Cold stress contributes to aberrant cytokinesis during male meiosis I in a wheat thermosensitive genic male sterile line

The male sterility of a wheat thermosensitive genic male sterile (TGMS) line is strictly controlled by temperature. When the TGMS line BS366 was exposed to 10 °C from the pollen mother cell stage to the meiosis stage, a few pollen grains were formed and devoid of starch. We report here a large-scale transcriptomic study using the Affymetrix wheat GeneChip to follow gene expression in BS366 line anthers in response to cold stress. Notably, many cytoskeletal signaling components were gradually induced in response to cold stress in BS366 line anthers. However, the cytoskeleton-associated genes that play key roles in the dynamic organization of the cytoskeleton were dramatically repressed. Histological studies revealed that the separation of dyads occurred abnormally during male meiosis I, indicating defective male meiotic cytokinesis. Fluorescence labelling and subcellular histological observations revealed that the phragmoplast was defectively formed and the cell plate was abnormally assembled during meiosis I under cold stress. Based on the transcriptomic analysis and observations of characterized histological changes, our results suggest that cold stress repressed transcription of cytoskeleton dynamic factors and subsequently caused the defective cytokinesis during meiosis I. The results may explain the male sterility caused by low temperature in wheat TGMS lines.