Comparative Analysis of Anther Transcriptome Profiles of Two Different Rice Male Sterile Lines Genotypes under Cold Stress.

Rice is highly sensitive to cold stress during reproductive developmental stages, and little is known about the mechanisms of cold responses in rice anther. Using the HiSeq™ 2000 sequencing platform, the anther transcriptome of photo thermo sensitive genic male sterile lines (PTGMS) rice Y58S and P64S (Pei'ai64S) were analyzed at the fertility sensitive stage under cold stress. Approximately 243 million clean reads were obtained from four libraries and aligned against the oryza indica genome and 1497 and 5652 differentially expressed genes (DEGs) were identified in P64S and Y58S, respectively. Both gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were conducted for these DEGs. Functional classification of DEGs was also carried out. The DEGs common to both genotypes were mainly involved in signal transduction, metabolism, transport, and transcriptional regulation. Most of the DEGs were unique for each comparison group. We observed that there were more differentially expressed MYB (Myeloblastosis) and zinc finger family transcription factors and signal transduction components such as calmodulin/calcium dependent protein kinases in the Y58S comparison group. It was also found that ribosome-related DEGs may play key roles in cold stress signal transduction. These results presented here would be particularly useful for further studies on investigating the molecular mechanisms of rice responses to cold stress.

[Transcriptome analysis of early interaction between rice and Magnaporthe oryzae using next-generation sequencing technology].

Magnaporthe oryzae is speculated to express and translocate a set of effector proteins to interfere with rice innate immunity and to promote its invasion. In this study, we carried out a transcriptome analysis of early interaction between rice and M. oryzae using a next generation sequencing technology to identify putative effector protein genes. We totally obtained 338 942 M. oryzae derived sequence tags from around 12.5 M gross mixed tags by referring the genome sequence of reference strain 70-15. These M. oryzae sequences were finally mapped to 779 predicted genes. Of these 799 genes, 108 were predicted to be involved in the interaction between rice and M. oryzae and 42 encoded proteins predicted to be secreted. Expression of these 42 putative secreted protein genes were further assessed using a reverse transcription polymerase chain reaction (RT-PCR) method, which revealed that 12 of them were expressed during the infection. Four of these 12 expressed genes were further confirmed to be expressed specifically during the infection. This study demonstrated an attempt to isolate M. oryzae genes, especially those putative effector protein genes, which are expressed specifically at the early interaction stage using a next-generation sequencing technology.

Relationship between grain yield and leaf photosynthetic rate in super hybrid rice.

In order to explore the relationship between grain yield and photosynthesis, the yield composition and leaf photosynthetic rate in some super hybrid rices and ordinary hybrid rice 'Shanyou 63' as control were measured in 2000-2005. The results were as follows. (1) The yield levels of the four super hybrid rices, 'Pei'ai 64S/E32', 'P88S/0293', 'Jin23A/611' and 'GD-1S/RB207', were significantly higher, being 108%-120% of 'Shanyou 63'. (2) These super hybrid rices had a better plant type with more erect upper layer leaves and bigger panicles or more spikelets per panicle, being 125%-177% of spikelets Shanyou 63 spikelets. (3) Net photosynthetic rates of these super hybrid rices were significantly higher in the second leaf but not necessarily in the first leaf or flag leaf than those of spikelets Shanyou 63 spikelets. (4) The removal of half flag leaf led to a decline in the seed-setting rate, while the removal of half panicle induced its increase in spikelets GD-1S/RB207 spikelets. Hence, higher yield in these super hybrid rices can be attributed to their bigger panicles, better plant type and higher light use efficiency of their canopies. Raising the photosynthetic capacity of each leaf, especially flag leaf, is the key to overcome the photosynthate-source restriction on grain yield and to make a new breakthrough of yield potential in future breeding of super hybrid rice.

[Fertility alteration of male sterile rice line annong S-1 and the expression of fertility related aprt gene].

The thermo-sensitive point and the thermo-sensitive stage for fertility alteration in the thermo-sensitive genic male sterile (TGMS) line Annong S-1 were studied. In nature environment and green house,the leaf, root and young panicle were treated by low and high temperature respectively. In total, 8 treatments were carried out. Results indicated that during the thermo-sensitive stage of fertility alteration, in high temperature environmental conditions, the low temperature treatment in the root did not significantly induce Annong S-1 to be fertile, while the low temperature treatment in young panicle obviously induced Annong S-1 to be fertile. Therefore, the thermo-sensitive point of Annong S-1 is the young panicle. The stage of fertility alteration was also investigated. Results indicated that alteration occurred in the phase from the formation of pollen mother cell to the tetrad of miosis. aprt gene is related the male sterility. The expression of aprt gene in root,young panicle and leaf were investigated by RT-PCR respectively. In young panicle, the expression of aprt gene was greatly down regulated by high temperature, while in root and leaf the expressions have no great changes. These data show that the young panicle is sensitive to temperature change. The result also supported that the young panicle is the thermo-sensitive point of Annong S-1 in the fertility alteration. These conclusions can be used to direct in hybrid rice seed production.