Visualizing Meiotic Chromosome Pairing and Segregation in Interspecific Hybrids of Rice by Genomic in situ Hybridization

Meiotic disturbances in F1 hybrids and their progenies are still major problems in wide hybridization.To investigate the genome affinity reflected in chromosome pairing and segregation,we studied chromosome behaviors during meiosis in two interspecific F1 hybrids[O.minuta×O.australiensis(Om×Oa,BCE genome)and Oa×O.ridleyi(Or,EHJ genome)]by using both traditional staining methods and genomic in situ hybridization(GISH).GISH analysis has been successfully performed on mitotic chromosomes to distinguish different Oryza genomes,but relatively fewer systematic analyses of meiotic chromosomes of interspecific hybrids have been reported.In the hybrids,highly irregular chromosome behaviors through meiosis resulted in producing microspores with unbalanced genome.At diakinesis of these two hybrids,most chromosomes present as univalent,with low frequency as bivalents and occasionally as trivalents.In a pollen mother cell,2 to 8 bivalents and 0 to 4 trivalents were observed in the hybrid Oa×Or,and 1 to 8 bivalents and 0 to 5 trivalents were observed in the hybrid Om×Oa.GISH results indicated that 51.52%bivalents in Oa×Or and 79.65%bivalents in Om×Oa involved allosyndetic association,which indicates that recombination and introgression should be possible if viable backcrosses can be recovered even from triploid hybrids.In this study,we revealed that the meiotic disturbance due to low affinities between parental genomes is the major reason for the sterility of these two triploid interspecific hybrids.The two hybrids showing vigor in reproductive growth are potential genetic resources in future breeding programs.A better understanding of genomic affinities between these distant Oryza species can facilitate planning an effective breeding program by using wide hybridization,and efficient and routine GISH analysis is helpful to monitor alien introgression in the process.

Cloning and Characterization of Protein Prenyltransferase Alpha Subunit in Rice

Protein prenylation plays a crucial role in plant development and stress response.We report the function of pren yltra nsferase a-sub unit in rice.Protein-protei n in teractions showed that the fam esyl-transferase(OsPFT)/geranylgeranyltransferase-l(OsPGGT l-a)protein interacted together with OsPFT-P and OsPGGT l-p.The a-and p-subunits of OsPFT formed a heterodimer for the transfer of a farnesyl group from famesyl pyrophosphate to the CaaX-box-containing peptide N-dansyl-GCVLS.Furthermore,the tissue expressi on patter ns of the OsPFT and OsPGGT I sub units were similar,and these sub units were localized in the cytoplasm and nucleus.Moreover,OsPFT/OsPGGT/-a-deletion homozygous rice mutants had a lethal phenotype,and the heterozygous mutants exhibited reduced pollen viability.These results indicated that prenylation plays an important role in rice development.

Self-incompatibility Characteristics of 34 Apricot Cultivars in Xinjiang

[ Objective] This study aimed to explore the relationship between self-incompatibility strength and characteristics related to pollination and fertilization of different apricot varieties in Xinjiang. [ Method] The pollen amount, pollen germination rate, pollen tube growth status and fruiting setting rate by self-pollina- tion of 34 apricot cultivars in Xinjiang were determined, to analyze the self-incompatibility of different apricot cultivars. [ Result] The average pollen amount per anther of 34 apricot eultivars was 1 213.7, and the average pollen germination rate was 46.0%. There were great differences in the self-incompatlbility of different cuhivars ; most pollen tubes of the euhivars with high self-incompatibility stopped elongating at 1/3 or 1/2 part of the styles, and only a few pollen tubes of the euhivars with low self-incompatibility reached the ovary, and the normal fertilization ratio was significantly lower than that in self-compatible cultivars. [ Conclusion] Among the 34 apricot cuhivars, only 6 cuhivars were self-compatible and the others exhibited gametophyte self-incompatibility. In addition, the fruit setting rate by self-pollination was low.

Impacts of high temperature,relative air humidity,and vapor pressure deficit on the seed set of contrasting maize genotypes during flowering

Heat stress is a major constraint to current and future maize production at the global scale.Male and female reproductive organs both play major roles in increasing seed set under heat stress at flowering,but their relative contributions to seed set are unclear.In this study,a 2-year field experiment including three sowing dates in each year and 20 inbred lines was conducted.Seed set,kernel number per ear,and grain yield were all reduced by more than 80%in the third sowing dates compared to the first sowing dates.Pollen viability,silk emergence ratio,and anthesis-silking interval were the key determinants of seed set under heat stress;and their correlation coefficients were 0.89^(***),0.65^(***),and-0.72^(***),respectively.Vapor pressure deficit(VPD)and relative air humidity(RH)both had significant correlations with pollen viability and the silk emergence ratio.High RH can alleviate the impacts of heat on maize seed set by maintaining high pollen viability and a high silk emergence ratio.Under a warming climate from 2020 to 2050,VPD will decrease due to the increased RH.Based on their pollen viability and silk emergence ratios,the 20 genotypes fell into four different groups.The group with high pollen viability and a high silk emergence ratio performed better under heat stress,and their performance can be further improved by combining the improved flowering pattern traits.