Search

The genus Nicotiana is an important germplasm source for cultivated tobacco varieties improvement, the creation of tobacco interspecific hybrids and their molecular cytological analysis during the meiotic phase will provide the basis for the subsequent efficient transfer and utilization of excellent wild germplasm. Allotriploid interspecific hybrids were created from the parents of Nicotiana sylvestris Q67 and common Nicotiana tabacum L. cv. K326. Their chromosome composition, chromosomal behavior during the meiosis and expression of related genes were investigated by routine cytological observation, genomic in situ hybridization and real-time quantitative PCR. In this study, 68 allotriploid hybrids (SST) with 36 chromosomes were identified by phenotypic and cytological analysis from crossing Nicotiana sylvestris with Nicotiana tabacum. The results of general cytology and genomic in situ hybridization showed that 29.26% of the pollen mother cells of interspecific hybrids were abnormal in meiosis. The main abnormal behavior was the backward chromosomes from the T chromosome group in metaphase I and II, with 1-3 lagging chromosomes. The cells with the most lagging types in metaphase I and II were the cells with 1 and 2 lagging T chromosomes respectively. They accounted for 29.09% and 30.88% of the total number of cells carrying backward chromosomes, respectively. The abnormal types of anaphase I, anaphase II and telophase II were mainly unequal segregation, backward chromosomes and micronucleus. In anaphase I, a variety of abnormal segregation ratios were counted, but the chromosome composition after segregation was still close to 2∶1 (S∶T). The results of RT-qPCR showed that in prophase I, except for the significant up-regulation of CDKA:5319 and CYCA:6720 from S chromosome group, the expressions of other genes were significantly down regulated. From the metaphase I to the telophase II, compared with the control, except that MIS12 and CDKA:0239 from T chromosome group had no significant changes, other genes（CENH3, CDKA:5319, CYCA:0111 and CYCA:6720）were significantly or extremely significantly up-regulated, indicating that the disorder expression of meiosis related genes may be causing the abnormality of meiosis. [ABSTRACT FROM AUTHOR]