Functional conservation of the meiotic genes SDS and RCK in male meiosis in the monocot rice

The Arabidopsis SDS （SOLO DANCERS） and RCK （ROCK-N-ROLLERS） genes are important for male meiosis, but it is still unknown whether they represent conserved functions in plants. We have performed phylogenetic analyses of SDS and RCK and their respective homologs, and identified their putative orthologs in poplar and rice. Quantitative real-time RT-PCR analysis indicated that rice SDS and RCK are expressed preferentially in young flowers, and transgenic RNAi rice lines with reduced expression of these genes exhibited normal vegetative development, but showed significantly reduced fertility with partially sterile flowers and defective pollens. SDS deficiency also caused a decrease in pollen amounts. Further cytological examination of male meiocytes revealed that the SDS deficiency led to defects in homolog interaction and bivalent formation in meiotic prophase I, and RCK deficiency resulted in defective meiotic crossover formation. These results indicate that rice SDS and RCK genes have similar functions to their Arabidopsis orthologs. Because rice and Arabidopsis, respectively, are members of monocots and eudicots, two largest groups of flowering plants, our results suggest that the functions of SDS and RCK are likely conserved in flowering plants.

Sex chromosomes behavior and G-banding treatment of male meiosis in nuptial gift-giving spiders of the family Trechaleidae

Preliminary genetic studies in Trechaleidae spider family show high variation in sex chromosomes and high heterocigocity,suggesting high chromatin plasticity.The trechaleids Paratrechalea ornata,Trechalea bucculenta and Trechaleoides biocellata are present in Uruguay.Males offering nuptial gifts during courtship have been reported in P.ornata and T.bucculenta but not in T.biocellata.Nuptial gifts are an inherited trait probably highly affected by environmental factors,which play an important role in gene expression.We hypothesize that this trait could be associated with tissue-specific genes existing in G-bands.We investigate the male meiosis in these 3 species,their sex chromosome system and the effects of G-banding on their chromosomes,and elucidate genetic differences among them.Meiotic stages of the 3 species were submitted to Giemsa-staining and G-banding treatments.We observed a haploid number of n=11 in P.ornata and n=13 in both T.bucculenta and T.biocellata.Males from the 3 species presented an X_(1)X_(2)0 sex chromosome system,which is suggested as ancestral in Araneae.In P.ornata and T.bucculenta,both sex chromosomes were together and aligned in parallel until the segregation during anaphase I.In contrast to these species,sex chromosomes of T.biocellata usually remained distant from each other until diakinesis when they were observed associated in parallel disposition.Interstitial G-bands were similar in P.ornata and T.bucculenta,and they both differed from those in T.biocellata.The special behavior of sex chromosomes in T.biocellata as well as the different G-banding pattern of this species suggests the existence of novel modifications in this species.

Defective callose walls and cell plates during abnormal meiosis cause male-sterility in the oat mutant zbs1

During meiosis in flowering plants,degradation of the callose wall in tetrads releases newly produced microspores,which develop into mature pollen grains.In this study,we identified zbs1,a male-sterile mutant of naked oat（Avena nuda L.）that displayed complete spikelet sterility due to inviable mature pollen.The abnormal pollen grains originated from microspores with a defective callose wall and cell plate during meiosis.The defective callose wall and cell plate of the zbs1 mutant were detected by the labeling of cell wall epitopes（β-1,3-glucan） with immunogold during meiosis,and an abnormal chromosome configuration was observed by propidium iodide staining.The mature pollen grains of the zbs1 mutant were irregular in shape,and abnormal germination was observed by scanning electron microscopy.Together,our results indicate that the cause of male sterility in zbs1 is abnormal meiosis.

Single-nucleotide polymorphisms in HORMAD1 may be a risk factor for azoospermia caused by meiotic arrest in Japanese patients

Genetic mechanisms are implicated as a cause of some male infertility, yet are poorly understood. Meiosis is unique to germ cells and essential for reproduction. The synaptonemal complex is a critical component for chromosome pairing, segregation and recombination. Hormadl is essential for mammalian gametogenesis as knockout male mice are infertile. Hormadl-deficient testes exhibit meiotic arrest in the early pachytene stage and synaptonema! complexes cannot be visualized. To analyze the hypothesis that the human HORMAD1 gene defects are associated with human azoospermia caused by meiotic arrest, mutational analysis was performed in all coding regions by direct sequence analysis of 30 Japanese men diagnosed with azoospermia resulting from meiotic arrest. By the sequence analysis, three polymorphism sites, Single Nucleotide Polymorphism 1 （c. 163A〉G）, SNP2 （c. 501T〉G） and SNP3 （c. 918C〉T）, were found in exons 3, 8 and 10. The 30 patients with azoospermia and 80 normal pregnancy-proven, fertile men were analyzed for HORMAD1 polymorphisms. Both SNP1 and SNP2 were associated with human azoospermia caused by complete early meiotic arrest （P〈0.0S）. We suggest that the HORMAD1 has an essential meiotic function in human spermatogenesis.