Peculiar phenomena of rDNA locus on chromosomes of some Chinese plants in Scilla scilloides

Abstract

ABSTRACT. Two molecular cytological phenomena such as NOR and/rDNA loci in the chromosome complement of Scilla scilloides were observed by in situ hybridization using rDNA probe. Most of the plants of the species collected in Shaanxi Province, the People's Republic of China were diploid of genome A that was characterized by a pair of satellited a 2 chromosomes carrying heavy rDNA signal at the secondary constriction comprising of constricted region and its adjacent chromosome arms at metaphase. At interphase the rDNA signals dispersed in the nucleolus with condensed signal body at terminal end. A plant of AA diploid showed that rDNA signal of one a 2 chromosome condensed through the cycle of respective division, whereas that of another a 2 chromosome showed the normal behavior. Another phenomenon occurred frequently in small B-chromosomes in S. scilloides. The diploid and tetraploid plants of the genome B collected in Jiangsu had several small B-chromosomes carrying condensed rDNA signal in addition to b 1 chromosomes with heavy rDNA signal at metaphase and interphase, suggesting rDNA of small B-chromosomes did not involve to nucleolus organization. Scilla scilloides is a complex species involving such two genomes as the genome A (x=8) and the genome B (x=9). The karyotype of each genome is revealed, and their polyploids and/or hybrids between two genomes are recognized by Araki (1971) and Haga and Noda (1976). Then, four different research approaches were performed in S. scilloides such as by respective scientists for genomic constitution of population (Araki 1972a, Ding et al. 1999, by cytogenetic analysis (Araki 1971), by cytogeographic studies in Japan (Ihara 1977), in Korea (Araki 1972b, 1985Choi and Bang 1990;Choi et al. 2004 ), and in China (Yu and Araki 1991;Yu et al. 1993;Ding et al. 1998) and by molecular cytogenetic analyses (Hizume et al. 1993; Araki 1994, 1996;Hizume and Shibata 2001;Choi et al. 2008). Two genomes are different not only in chromosome number and karyotype, but also in genomic DNA level, revealed clearly by genomic in situ hybridization (Hizume and Araki 1996). Then, S. scilloides is useful to study genome differentiation, because they have differences between A and B genomes in genome structure/karyotype and their genomic DNA differentiation. In the present study two phenomena concerning rDNA loci/NORs by in situ hybridization (ISH) using rDNA probe are described for the first time. Ding et al. (1998). Plants were raveled and cultivated in pots and maintained in the experimental garden of Ehime University. Root tips were collected and treated in 2mM 8-hydroxiquinoline for 3h. Then, they were fixed in acetic-ethanol (1:3, volume ratio) and used immediately for observation or stored in a deep freezer until use. KEYWORDS: MATERIALS AND METHODS Thirty plants of Scilla scilloidesThe fixed root tips were soaked in 45% acetic acid for 5 min, treated in 45% acetic acid at 60°C for 8 min and transferred in cold 45% acetic acid. Then, they were squashed in 45% acetic acid under cover slips on...

Multiple Origin of Amphidiploids in the Complex Species of <i>Scilla scilloides</i>, Asparagaceae

“…A variation of AA diploids among populations would be explained by a change of amount of repetitive sequences and/or of nucleotide sequence (include change of base composition) of the repetitive DNA causing genomic differentiation detected by GISH and Southern hybridization of 5S rDNA in the diploids among localities as reported by Shibata et al (2017). Some variations of genome size in populations might be explained by a presence of small B-chromosomes reported frequently in Korean and Chinese popu-lations (Araki 1985, Yu and Araki 1991, Choi and Bang 1990, Ding et al 1998, Choi et al 2004, Hizume et al 2014. The AA diploids from Gansu China and Huashan China had nearly same genome size of the BB diploids and only the Korean AA diploids showed 1.3 times larger genome size than other diploids (Table 7, Shibata et al 2017).…”

Karyotypes of Amphidiploid of <i>Scilla scilloides</i> Complex in Taiwan with Special Reference to Secondary Constriction of the A Genome

“…The phenomenon might occur also between Okinawa Island and Kagoshima, Kyushu. The third hypothesis is that NOR function of Taiwan AABB plants was suppressed by unknown mechanism reported in a Chinese AA plant (Hizume et al 2014). In AABB population of Taiwan suppression of NOR activity of rDNA might occur partially on a 2 chromosomes by similar genetic condensation.…”

Karyotype evolution in conifers

“…The banding patterns not only facilitate chromosome identification but also in determining the species relationships. The peculiar feature of Larix species not observed in any other Pinaceae genus is the presence of proximal DAPI band on only one arm of some chromosomes, their number however, varies in different species (Hizume et al, 1988b(Hizume et al, , 1993a(Hizume et al, , 1994(Hizume et al, , 1998aGoryachkina et al, 2013) (Table 3, Fig. 2).…”

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