坛紫菜与长紫菜种间杂交后代的细胞崩溃现象与成活后代的表现型观察比较

坛紫菜壳孢子萌发的第一次和第二次分裂为减数分裂,结束后形成了一个基因型不同的四分体,随后由这个四分体发育成一个基因型嵌合的叶状体。由坛紫菜与长紫菜种间杂交所产生的杂合丝状体成熟后释放出壳孢子,后者在分裂初期出现了大量的细胞崩溃死亡,通过对单个的壳孢子萌发体进行定点跟踪观察后发现,细胞崩溃死亡不仅会发生在减数分裂的直接产物即处于二细胞期、三细胞期、四细胞期的萌发体,当细胞数大于4个的萌发体在进行有丝分裂时也会出现细胞崩溃死亡。绝大部分的壳孢子能进行第一次减数分裂,形成处于二细胞期的萌发体,随后进行第二次减数分裂,形成处于三细胞期或四细胞期的萌发体。培养4 d,78.6%的壳孢子已发育成含2~4个细胞的萌发体,其余为未分裂的壳孢子萌发体;在含2~4个细胞的萌发体中未出现细胞崩溃死亡的萌发体的百分率为99.7%,0.3%的个体出现了细胞崩溃死亡。随着培养时间的延长,大多数处于二细胞期的萌发体发育成处于三细胞期和四细胞期的萌发体,而大规模的细胞崩溃死亡也出现在处于三细胞期和四细胞期的萌发体中。培养14 d,处于三细胞期和四细胞期的萌发体的百分率分别为38.6%和37.2%,它们当中含有崩溃死亡细胞的个体百分率分别为99.5%和99.2%。此外,8.9%的萌发体能够发育成含4个以上细胞的个体,但在随后的有丝分裂中也出现了细胞崩溃死亡现象。培养35 d,大部分的萌发体其体细胞已全部崩溃死亡,但仍有约1%的萌发体能成活下来,可它们并非是由一个完整的四分体发育而来,而是由四分体中的1~2个成活细胞发育而来。培养45 d,可把成活体的形态和颜色分成类亲本型和重组型两大类。研究表明,利用紫菜种间杂交的后代在壳孢子萌发初期会出现细胞崩溃死亡的现象,不仅可以用于辅助更精确地鉴别物种,而且可以从其成活后代中筛选出具有重组优势的新品系。

Phenomenon of cell breakdown and phenotypic observation on surviving blades in interspecific hybridization progeny between Pyropia haitanensis and Pyropia dentata

In Pyropia haitanensis, meiosis occurs during the first two divisions of germinating conchospores, and then the latter formed a tetrad with diffierent genotype, finally the tetrad developed into a genotype chimeric blade. The heterozygous conchocelies was formed in the interspecific hybridization between Pyropia haitanensis and Pyropia dentata, which could produce conchospores after maturation, but the conchospores had serious cell breakdown at the early development stage of germination. Through the tracking observation of single conchospore germling, we found that cell breakdown occurred not only in the direct products of meiosis (dyad, triad and tetrad), but also in the mitosis when the number of germling cell was more than 4. In culture, most of the conchospores could form dyad after the first meiotic division, and then form triad or tetrad through the second meiotic division. When cultured for 4 days, 78.6% of the conchospores had developed into germlings containing 2-4 cells, and the rest were undivided conchospores; The percentage of germlings containing 2-4 cells that did not have dead cells was 99.7%, and 0.3% of individuals had dead cells. With the prolongation of culture time, most of the dyads developed into the triads and tetrads, while large-scale cells breakdown appeared in the triad and tetrad. After culture for 14 days, the percentages of triad and tetrad were 38.6% and 37.2%, respectively, in which 99.5% and 99.2% contained dead cells, respectively. In addition, 8.9% of the germlings could develop into individuals with more than 4 cells, but cell death also appeared in the subsequent mitosis. When cultured for 35 days, most of the cells of germlings had all died, still, about 1% of the germlings survived, but they did not develop from the complete tetrads, just developed from 1-2 surviving tetrad cells. After 45 days of culture, the surviving individuals could be divided into parental and recombinational type based on their morphology and color. The results confirmed that the hybrid breakdown occured in the early development stage of conchospores in interspecific hybridization of Pyropia, which could not only be used to assist in the more accurate identification of species, but also we could select new strains with recombination advantage from the surviving offspring.