Mechanism of Sterility and Breeding Strategies for Photoperiod/Thermo-Sensitive Genic Male Sterile Rice

To understand the male sterility mechanism of photoperiod/thermo-sensitive genic male sterile [P（T）GMS] lines in rice, the research progress on genetics of photoperiod and/or temperature sensitive genic male sterility in rice was reviewed. A new idea was proposed to explain the sterility mechanism of P（T）GMS rice. The fertility transition from sterile to fertile is the result of cooperative regulation of major-effect sterile genes with photoperiod and/or temperature sensitive genes, but not the so-called pgms gene in P（T）GMS rice. The minor-effect genes, which exhibit accumulative effect on sterility, are the important factors for the critical temperature of sterility transition. The more minor-effect genes the sterile line holds, the lower the critical temperature of sterility transition is. The critical temperature of sterility transition will be invariable if all the minor-effect genes are homozygous. The strategies for breeding P（T）GMS rice were also proposed. The selective indices of critical photoperiod and temperature for sterility transition should be set according to varietal type and ecological region. Imposing selection pressure is a key technology for breeding P（T）GMS rice with lower critical temperature for sterility, and improving the comprehensive performance of the whole traits and combining ability is vital for breeding P（T）GMS rice lines.

Genetic Analysis and Primary Mapping of pms4, a Photoperiod-Sensitive Genic Male Sterility Gene in Rice (Oryza sativa)

To understand the genetic characteristics of a new photoperiod-sensitive genic male sterile line Mian 9S, some reciprocal crosses were made between Mian 9S and six indica rice materials, Yangdao 6, Luhui 602, Shuihui 527, Mianhui 725, Fuhui 838 and Yixiang 1B. Genetic analysis results suggested that the photoperiod-sensitive genic male sterility （PGMS） of Mian 9S was controlled by a single recessive nuclear gene. Thus, the F2 population derived from the cross of Yangdao 6/Mian 9S was used to map the PGMS gene in Mian 9S. By using SSR markers, the PGMS gene of Mian 9S was mapped on one side of the markers, RM6659 and RM1305, on rice chromosome 4, with the genetic distances of 3.0 cM and 3.5 cM, respectively. The gene was a novel PGMS gene and designated tentatively as pms4. In addition, the application of the pms4 gene was discussed.

Immunohistochemical Analysis of IAA in Anthers of the Photoperiod-sensitive Genic Male-sterile Rice

The immunohistochemical localization of IAA and the comparison of their relative levels were carried out for the first time in the anthers of Nongken 58S and its wild type Nongken 58 (Oryza sativa subsp. japonica) after long_day and short_day treatments. The distribution of free_IAA in anthers and its dynamic variation could be reflected by this method. The results showed that the IAA level in the anthers of Nongken 58S after long_day treatment was much lower than that in short_day_treated Nongken 58S and those in wild type Nongken 58 in five stages from pistil and stamen primordia formation to late uninucleate stage. The possible reasons for IAA deficiency in Nongken 58S_LD anthers and its relationship with fertility alteration were also discussed.

Comparative Studies on the Changes of Microtubule Distribution and Reorganization During the Meiotic Stages of Development in Normal (IR36) and a Temperature/photoperiod Sensitive Male Sterile Line (Peiai 64S) of Rice ( Oryza sativa )

Changes in the pattern of organization of microtubules in the meiotic stages of development of pollen (i.e. from pre-meiotic interphase to more or less metaphase I) of a normal (IR36) and a temperature/photoperiod sensitive male sterile line (Peiai 64S) of rice were studied using immunofluorescence confocal microscopy. In IR36, from pre-meiotic interphase to metaphase I, the pattern of microtubule distribution in the meiocytes underwent a series of changes. Some new organizational patterns of microtubules (that have not been described before) were observed during microsporogenesis, including the existence of a broad band of perinuclear microtubules at the diakinesis stage of development. The pattern of microtubule distribution in the meiocytes of the male sterile line, Peiai 64S, was quite different front that seen in IR36. In Peiai 64S, the microtubules showed abnormal patterns of distribution from pre-meiotic interphase to metaphase I. For example the broad band of perinuclear microtubules seen at diakinesis in IR36 was much disorganized and loosened in Peiai 64S. The spindles formed were also very abnormal and different from the normal spindle. The appearance of abnormal microtubule distribution in the early stages of microsporogenesis may contribute to the malformation and ultimate abortion of pollen in Peiai 64S.

Preliminary Studies on the Effect of Photoperiod and Temperature on Male Fertility of a Cytoplasmic Male Sterile Line in Wheat

[Objective] The study aimed to reveal the effect of photoperiod and temperature on male fertility of cytoplasmic male sterile line Vtai911289a in wheat and discuss the mechanism of male fertility alteration. [ Method ] The sowing-date tests and designed conditions were conducted during 2003 -2005. [ Result] Fertility of Vtai911289a, could alter under specific photoperiod and temperature conditions. Temperature is one of the main factors influencing male fertility of the male sterile lines. Vtai911289a, showed stable sterility under the condition of the mean of daily temperature at fertility sensitive stage lower than 19℃ and presented partial fertility when the mean of daily temperature at fertility sensitive stage lower than 20 - 22℃. Photoperiod to some extent affects the male fertility of Vtai911289a, long-day condition is helpful for the male fertility of the sterile line. [ Conclusion] The application of photoperiod temperature-sensitive cytoplasmic male sterile line in production has a higher safety than that of temperature sensitive sterile line.

Isolation and Analysis of the Promoter of OsRacD from PhotoperiodSensitive Genic Male Sterile Rice

By using OsRacD cDNA as probe to screen the genomic library of photoperiod sensitive genic male sterile rice line Nongken 58S, a positive clone containing 2 kb promoter and 396 bp coding region of OsRacD was obtained. Compared with the promoter of OsRacD cloned by reverse PCR from normal rice variety Nongken 58 （Nongken 58N）, the homology was 99.8%, and the different nucleotides were outside the predicted response elements in promoter, suggesting that the fertility between rice varieties Nongken 58S and Nongken 58N under the long-day conditions was not attributed to the difference in the structure of OsRacD upstream regulation sequences, but to the developmental regulation of gene differential expression.

Studies on the Photoperiod Sensitive Characters of Male Fertility Alteration of Peiai64S' Main Male Genic Sterile Gene

Peiai64S, an indica male sterile rice with a male fertility alteration under different environments, is selected from the offspring of indica rice crossed with Nongken58S. Nongken58S, a japonica pho-toperiod sensitive genie male sterile rice (PGMS), deriving from a natural mutant plant individual of normal japonica rice variety, Nongken58, is used as a male sterile gene donor of Peiai64S. But Peiai64S is not a typical PGMS rice, the male fertility is sensitive to temperature just as thermo-sensitive genie male sterile rice (TGMS). We have selected typical PGMS plants in F2 population of Peiai64S× Nongken58, whose ratio of fertile plants to sterile plants is nearly 3:1. The sterility inheritance conformed to one pair of gene segregation model. The result indicates the main male sterile gene in Peiai64S is not other than the PGMS gene, and comes from Nongken58S. The genetic background affects effective expression of the PGMS gene. This suggests that we ought to focus on optimizing the genetic background of the PGMS gene in PGMS rice breeding, and select an ideal genetic background as a transgenic background in molecular breeding.

pms3 is the locus causing the original photoperiod-sensitive male sterility mutation of‘Nongken 58S'

Photoperiod-sensitive genie male sterile (PSGMS) rice is a very useful germplasm for hybrid rice development. It was first found as a spontaneous mutant in a japonic a cultivar 'Nongken 58' . pms3 on chromosome 12 was determined to be the locus where the original PSGMS mutation occurred, changing the normal cultivar Nongken 58 to PSGMS Nongken 58S. Large amounts of RAPD and AFLP analyses were also conducted for the fine mapping of the pms3 genomic region, which resulted in 4 molecular markers linked to pms3. Although these markers somewhat increased the marker density of this region, the pms3 locus is still located in a marker-sparse region.

Long non-coding RNAs play an important role in regulating photoperiod-and temperature-sensitive male sterility in rice

Rice(Oryza sativa L.)is a major food crop for more than half of the world’s population.Therefore,increasing rice production is of great importance.The successful development of hybrid rice in the 1970s was an important achievement for increasing yield potential,since hybrid rice varieties produce higher yields than inbred varieties(Cheng et al.,2007).In plants,male sterility refers to the inability of producing dehiscent anthers and functional pollen(Chen and Liu,2014).

Progresses and Strategies of Gene Mapping and Isolating of Photo(thermo) sensitive Genic Male Sterile Rice

Considering the research on classical genetics of photoperiod(therm) sensitive genic male sterile rice, it is important to select the sterile lines and their segregating population controlled by one pair of gene in mapping and isolating sterile genes. It is discussed the advantages, disadvantages and the reasons leading to various mapping results of chromosome location of sterile genes through gene marker, isozyme marker and DNA marker techniques. In comparison to isolation of photo(thermo) sensitive sterile genes via various plant gene cloning techniques, it was concluded that map based cloning was acceptable, but it is still difficult to locate the loci of sterile genes within 1cM. On the other hand, “sensitivity to environment”, an important characteristic of sterile lines can be fully utilized by DD PCR and (or) RDA techniques. Therefore, these two techniques were considered as the effective ways to isolate sterile genes.

Fine mapping and candidate gene prediction of the photoperiod and thermo-sensitive genic male sterile gene pms1(t) in rice

Pei＇ai64S, an indica sterile variety with photoperiod and thermo-sensitive genic male sterile （PTGMS） genes, has been widely exploited for commercial seed production for ＂two-line＂ hybrid rice in China. One PTGMS gene from Pei＇ai64S, pmsl（t）, was mapped by a strategy of bulked-extreme and recessive-class approach with simple sequence repeat （SSR） and insert and deletion （In-Del） markers. Using linkage analysis for the F2 mapping population consisting of 320 completely male sterile individuals derived from a cross between Pei＇ai64S and 93-11 （indica restorer） lines, the pmsl（t） gene was delimited to the region between the RM21242 （0.2 cM） and YF11 （0.2 cM） markers on the short arm of chromosome 7. The interval containing the pmsl（t） locus, which was co-segregated with RM6776, is a 101.1 kb region based on the Nipponbare rice genome. Fourteen predicted loci were found in this region by the Institute for Genomic Research （TIGR） Genomic Annotation. Based on the function of the locus LOC_Os07g12130 by bioinformatics analysis, it is predicted to encode a protein containing a Myb-like DNA-binding domain, and may process the transcript with thermosensory response. The reverse transcription-polymerase chain reaction （RT-PCR） results revealed that the mRNA levels of LOC_Os07g12130 were altered in different photoperiod and temperature treatments. Thus, the LOC_Os07g12130 locus is the most likely candidate gene for pmsl（t）. These results may facilitate not only using the molecular marker assisted selection of PTGMS genes, but also cloning of the pmsl（t） gene itself.

Temperature-sensitive splicing is an important molecular regulation mechanism of thermosensitive genic male sterility in rice

Photoperiod and temperature-sensitive genetic male sterility (PGMS and TGMS) plants have a number of desirable characteristics for hybrid production. Two-line hybrids developed using the PGMS/TGMS system now account for a large proportion of rice production in China. In this paper, we summarize recent advances on molecular regulation mechanisms and genetics of PGMS/TGMS in rice. We suggest that temperature-sensitive splicing, an important posttranscriptional regulatory mechanism in modulating gene expression and eventually development and differentiation, is also an important molecular regulation mechanism of TGMS in rice. We review those factors involved in temperature-sensitive splicing like cis splice site, snRNA, trans premRNA splicing protein and SR proteins, and delineate that splicing could be regulated by a complex cell signaling pathway. These might shed light on other unknown molecular PGMS/TGMS mechanisms.

Selection and Characterization of a Novel Photoperiod-Sensitive Male Sterile Line in Upland Cotton

Upland cotton （Gossypium hirsutum L.） shows strong heterosis. However, heterosis is not widely utilized owing to the high cost of hybrid seed production. Creation of a photoperiod-sensitive genetic male sterile line could substantially reduce the cost of hybrid seed production in upland cotton. Such a mutant with virescent marker was found by space mutation in near-earth orbit and its traits had been stable after 4 years of selection in Anyang and Sanya, China. This mutant was fertile with an 11-12.5 h photoperiod when the temperature was higher than 21.5 ℃ and was sterile with a 13-14.5 h photoperiod. Genetic analysis indicated that both traits were controlled by a single recessive gene or two closely linked genes. Also, the cytological observations and transcriptome profiling analysis showed that the degradation of pollen grain cytoplasm should be the primary reason why the mutant line were male sterile under long-day conditions.

Gene expression profiling under different photoperiod/temperature conditions in a photoperiod-/thermo-sensitive genic male sterile line of rice(Oryza sativa L.)

Peiai 64S is a photoperiod- and thermo- sensitive genic male sterile (PTSGMS) line of rice, which is male sterile at long day/high temperature and partial fertile at short day/low temperature. A cDNA array representing 3328 unique rice genes was used to profile the gene expression patterns in the young panicles of Peiai 64S under these two condi- tions. The statistical data showed that up to 14.60% of genes exhibited up-or down-regulated expressions in the plants at long day/high temperature compared with plants at short day/low temperature. Only four genes were up-regulated while 482 genes down-regulated. Real-time PCR with all the up-regulated and 9 randomly selected down-regulated genes confirmed the differential expressions detected by the array, indicating that the constructed cDNA array is reliable. These differently expressed genes participated in almost all cell biological responses. Analysis of up- and down-regulated genes revealed distinctive changes between the mRNA abundances of MMK1 and MMK2, both of which are analogs ofMAPK, and significant down-regulation of several transcription factors. It was suggested that changes that occurred in the MAPK signal transduction path- way might disturb the transcription control necessary for morphogenesis of pollens and corresponding phys- iological functions.

Identifying and mapping cDNA fragments related to rice photoperiod sensitive genic male sterility

The differentially expressed cDNA fragments have been obtained by differential screening with cDNA-RAPD technique in photoperiod sensitive genic male sterile (PGMS) rice. Some of them have been reassessed with Northern blot hybridization, from which a PGMS-related positive fragment, RPG43, has been identified. Further analysis on RPG43 with Southern blot and RAPD indicates that the fragment is a single-copy sequence and its mRNA has been processed after transcription. Sequence analysis reveals that RPG43 is 744 bp in length and contains a 60 bp region (from 126th to 185th bp) showing 72% homology to a human DNA sequence, pac pDJ-356d6, on chromosome 11. So it is a new sequence found in plant and its GenBank access number is AF126027. In addition, RPG43 has been mapped to a position 3.8 cM away from RFLP marker R1553 on chromosome 5 of rice.

光/温敏核不育系的不育机理及两系杂交稻的发展与展望

本文回顾了中国两系杂交水稻的发展历史;介绍了两系法中光/温敏型核不育系遗传资源的发现和选育;总结了植物中光温敏型雄性不育的遗传学和细胞学机制;并对水稻两系法中光/温敏型雄性不育系的遗传资源优化及育种策略提出了建议。

光敏核不育水稻的光温反应研究——Ⅱ.人工控制条件下粳型光敏不育系的育性鉴定

在人工控制条件下研究了光照时间和温度对农垦58S及以此为基因源转育的其他粳型光敏不育系育性的影响。结果表明,供试粳型光敏不育系的育性受光照时间和温度的双重影响,在15.0h光长与29.6℃平均温度(最高与最低温度分别为33.0℃与28.0℃)的长光照高温条件下,自交结实率为0或接近于0;在12.0h光长与23.6℃平均温度(27.0/22.0℃)的短光照低温条件下,自交结实率较高;在长光低温(15.0h/23.6℃)和短光高温(12.0h/29.6℃)下,育性出现不同程度的转变。不同材料的育性对光温反应存在着差异,提示遗传背景对育性表达可能有重要作用。本研究结果有助于对自然条件下光敏不育系夏季制种纯度不高而秋季警种产量又较低的现象在理论上给予合理的解释。

温度敏感型雄性不育水稻的鉴定

在人工控制条件下应用两因子完全随机区组设计研究了籼型5460不育系对温度与光照的反应。结果表明参试的5个对照品种(系)的育性在所有处理中都表现正常,而5460不育系在日最高/最低温度为27/22℃、平均为23.5℃时,不论光照时间为12.0h、13.5h 还是15.0h/日,其花粉育性与套袋自交结实率都基本正常,在33/28℃,平均为29.5℃时,不论光照如何,大部分植株表现为完全不育或高度不育。套袋自交结实率的方差分析表明,光照长度引起育性变化的差异不显著,不同温度间的差异极显著,光温互作效应也达到显著水平。试验表明5460不育系是“温度敏感型”的雄性不育系。这一结论与1987年福州地区的气象资料和5460不育系在当时当地的实际育性变化相符合。讨论了温度敏感型雄性不育水稻对理论研究和育种实践的价值。

光敏核不育水稻的光温反应研究 Ⅲ.减数分裂期温度对两个籼稻光敏不育系育性转换的影响

在人工控制条件下研究了在15小时长光照下减数分裂期的不同温度(23.3～30.3℃)对籼稻光敏不育系W6154S和5460S育性转换的影响。结果表明,温度对育性的影响因温度的高低及处理持续时间长短而异,不同的材料对温度的反应不同。5460S从不育转为可育的临界温度在26.4℃左右,而W6154S在处理温度范围内均出现自交结实现象,表明供试的W6154S株系育性转换的临界温度可能超过30.3℃。提出了深入研究影响籼稻光敏不育系育性转换的临界温度的建议。

W6154S×农垦58杂交后代育性转换株的发育感光性与育性转换特性

为了探讨水稻发育感光性与光、温敏雄性不育性之间的遗传关系,对W6154S/农垦58杂交组合F_2中发育感光性不同而具有明显育性转换特性的不育株及其衍生的F_3株系各单株进行了发育感光性与育性转换光温反应特性鉴定。结果表明:W6154S的育性转换特性可在发育感光性不同的背景中表达光敏不育性;所有F_2、F_3的育性转换株中没有分离出典型的温敏不育株;育性转换性状能在低世代稳定,而控制育性转换光温条件的遗传基础是复杂的。发育感光性强弱不是育性光敏性强弱的决定因子,育性光敏性强弱受遗传背景多因子综合作用,农垦58及其类似背景中可能存在增强光敏雄性不育主效基因表达的遗传因子。