Dhar Manoj K, Kour Gurmeet, Kaul Sanjana
School of Biotechnology, University of Jammu, Jammu-180006, INDIA.
Comp Cytogenet. 2017 May 22;11(2):375-392. doi: 10.3897/CompCytogen.11i2.11779. eCollection 2017.
is a diploid (2n = 2x =12) weed belonging to family Plantaginaceae. We reported a novel B chromosome in this species composed of 5S and 45S ribosomal DNA and other repetitive elements. In the present work, presence of B chromosome(s) was confirmed through FISH on root tip and pollen mother cells. Several experiments were done to determine the transmission of B chromosome through male and female sex tracks. Progenies derived from the reciprocal crosses between plants with (1B) and without (0B) B chromosomes were studied. The frequency of B chromosome bearing plants was significantly higher than expected, in the progeny of 1B female × 0B male. Thus, the B chromosome seems to have preferential transmission through the female sex track, which may be due to meiotic drive. One of the most intriguing aspects of the present study was the recovery of plants having more chromosomes than the standard complement of 12 chromosomes. Such plants were isolated from the progenies of B chromosome carrying plants. The origin of these plants can be explained on the basis of a two step process; formation of unreduced gametes in 1B plants and fusion of unreduced gametes with the normal gametes or other unreduced gametes. Several molecular techniques were used which unequivocally confirmed similar genetic constitution of 1B (parent) and plants with higher number of chromosomes.
是一种属于车前科的二倍体（2n = 2x = 12）杂草。我们报道了该物种中一种由5S和45S核糖体DNA以及其他重复元件组成的新型B染色体。在本研究中，通过对根尖和花粉母细胞进行荧光原位杂交（FISH）证实了B染色体的存在。进行了多项实验以确定B染色体通过雄性和雌性生殖途径的传递情况。对具有（1B）和不具有（0B）B染色体的植株之间正反交产生的后代进行了研究。在1B雌性×0B雄性的后代中，携带B染色体的植株频率显著高于预期。因此，B染色体似乎通过雌性生殖途径优先传递，这可能是由于减数分裂驱动。本研究最有趣的方面之一是发现了染色体数目超过标准的12条染色体的植株。这些植株是从携带B染色体的植株后代中分离出来的。这些植株的起源可以基于一个两步过程来解释；1B植株中未减数配子的形成以及未减数配子与正常配子或其他未减数配子的融合。使用了几种分子技术，明确证实了1B（亲本）和染色体数目较多的植株具有相似的遗传组成。
