Au Elements and Their Evolution in Some AIIopolyploid Genomes of Aegilops

To study the sequences of short interspersed nuclear elements （SINEs） evolution in some allopolyploid genomes of Aegilops, 108 Au element fragments （a novel kind of plant SINE） were amplified and sequenced in 10 species of Aegilops, which were clustered into three different groups （A, B and C） based on their related geuome types. The sequences of these Au element fragments were heterogouous in di-, tetra-, and hexa-ploids, and the deudrograms of Au element obtained from phylogenetic analysis were very complex in each group and could be clustered into 15, 15 and 22 families, respectively. In this study, three rules about Au elements evolution have been drawn from the results： i. Most families were composed of Au element members with different host species in three groups; ii. Family 1-6 in Group A, Family 1-6 in Group B, Family 1-4 and Family 6-13 in Group C contained only one, apparently highly degenerate Au dement member （a single representative elemeut）; iii. Elements generally fell into clades that were species-specific with respect to their host species. The potential mechanisms of Au element evolution in Aegilops were discussed.

Atomic force microscopic view of the fine topography on the tobacco stigma surface during its response to pollination

During compatible pollination in tobacco, an extracellular matrix (ECM) is secreted from the stigma surface; however, it is unknown whether the pattern of secretion across the stigma depends on the pollen source. In fact, technical limitations have prevented clear observation of ECM secretion. Here, we report the detailed topographic changes on the stigma surface that accompanies intraspecies and interspecies pollination in tobacco using contact mode atomic force microscopy (AFM). Our results, which show the dynamics and time course of ECM secretion after pollination, indicate that a certain pattern of secretion already exists on the stigma prior to pollination. Intraspecies induced a two-step response, characterized by topographical changes on the stigma surface several hours after pollina-tion, which was distinct from the pattern of ECM secretion induced by interspecies pollination. This difference was confirmed by root-mean-square analysis, which assessed the roughness of the stigma surface. Our findings indicate that compatible pollination not only induces ECM secretion from the stigma, but also results in a specific distribution of the ECM. Thus, this study demonstrates the pow-erful potential of AFM in studying the pollen-stigma interaction.

Characterization and Use of Male Sterility in Hybrid Rice Breeding

The hybrid rice （Oryza sativa L.） breeding that was Initiated In China in the 1970s led to a great improvement in rice productivity. In general, It increases the grain yield by over 20% to the inbred rice varieties, and now hybrid rice has been widely introduced into Africa, Southern Asia and America. These hybrid varieties are generated through either three-line hybrid and two-line hybrid systems; the former is derived from cytoplasmic male sterility （CMS） and the latter derived from genlc male sterility （GMS）. There are three major types of CMS （HL, BT and WA） and two types of GMS （photoperlod-sensitlve （PGMS） and temperature-sensitive （TGMS））. The BT- and HL-type CMS genes are characterized as orf79 and orfH79, which are chimeric toxic genes derived from mltochondrial rearrangement. Rf3 for CMS-WA Is located on chromosome 1, while Rf1, Rf4, Rf5 and Rf6 correspond to CMS-BT, CMSoWA and CMS- HL, located on chromosome 10. The Rfl gene for BT-CMS has been cloned recently, and encodes a mltochondriatargeted PPR protein. PGMS Is thought to be controlled by two recessive loci on chromosomes 7 and 12, whereas nine recessive alleles have been identified for TGMS and mapped on different chromosomes. Attention Is still urgently needed to resolve the molecular complexity of male sterility to assist rice breeding.

Physical location of rice Gm-6,Pi-5(t) genes in O.officinalis with BAC-FISH

A fluorescence in situ hybridization (FISH) procedure was adopted to physically map two rice BAC clones 24E21 and 4F22 linked to Gm-6 and Pi-5(t) in O. offi-cinalis. FISH results showed that the two BAC clones were located at 4L. The percentage distance from the centromere to the hybridization sites was 72 ± 2.62 for 24E21 and 54± 5.43 for 4F22, the detection rates were 52.70% and 61.2%. The results obtained from the BAC and plasmid clones, RG214 and RZ565 of cultivated rice and O. officinalis were the same. This suggested that the markers, RG214 and RZ565 of cultivated rice and O. officinalis were in the same BAC clones. The homologous sequences of Gm-6 and Pi-5(t) in O. officinalis were positions that signals existed on the 4L. Many signals were observed when no Cot-1 DNA blocked. This also showed that repetitive sequences were some ho-molgous between cultivated rice and O. officinalis. The identification of chromosome 4 of O. officinalis is based on Jena et al. (1994). In our study, we discussed

The editing sites in transcripts of functional genes of rice mitochondria

RNA editing exists extensively in the higher plant mitochondria, and is a required step for forming functional proteins. There may be some relationship between RNA editing and cytoplasmic male sterility (CMS), a kind of phenomenon that is attributed to mitochondrial genome mutations. The research materials used are the gametophytic male sterility line (A), maintainer line (B) and F1 hybrid (F1) of HL-type CMS rice. cDNAs and DNAs of atp6 and coxII have been obtained from A, B and F1 by PCR and RT-PCR. Comparing sequences of cDNAs and DNAs, 18 and 15 editing sites were found respectively in the transcripts of atp6 and coxll. A, B and F1 shared the same editing sites. RNA editing improves hydrophobicity and conservation of the predicted protein as compared with other organisms.

Mediation of flowering by a calmodulin-dependent protein kinase

A calmodulin-dependent protein kinase (MCK1) appeared important in regulating flowering in tobacco. The expression of modified MCK1 that lacks the C-terminal including calmodulin-binding domain upsets the flowering developmental program, leading to the abortion of flower primordia initiated on the main axis of the plant and, as well, caused the prolongation of the vegetative phase in axillary buds. The abortion process of flowers began first in the developing anthers and subsequently the entire flower senesces. In axillary buds the prolonged vegetative phase was characterized by atypical elongated, narrow, twisted leaves. These results suggested a role for calmodulin-dependent protein kinase homologs in mediating flowering.

Technological exploration of BAC-FISH on mitotic chromosomes of maize

The rice BAC-DNA was used as probes and fluorescence in situ hybridization(FISH)was applied to the interphase and metaphase mitotic chromosomes of maize.To optimize the BAC-FISH technique,we respectively assayed the effect of several factors,including maize or rice genomic C_(o)t DNA used as blocking reagent of DNA,washing temperatures and FAD concentration in the washing buffer and in the hybrid solution.The results show that C_(o)t DNA of maize genome blocked the repetitive sequence of the rice BAC-DNA when the C_(o)t value was below 50.Meanwhile,it was necessary to adjust the C_(o)t value according to the different probes and their ratios.Decreasing the concentration of FAD in the hybridization mixtures,adjusting the washing rate after hybridization,and most especially,blocking the ricespecific repetitive sequences of BAC-DNA could improve the positive signals of BAC-FISH.