Raghavan V
J Cell Biol. 1981 Jun;89(3):593-606. doi: 10.1083/jcb.89.3.593.
The distribution of poly(A)-containing RNA [poly(A)+RNA] in pollen grains of Hyoscyamus niger during normal gametophytic development and embryogenic development induced by culture of anther segments was followed by in situ hybridization with [3H]-polyuridylic acid as a probe. No binding of the isotope occurred in pollen grains during the uninucleate phase of their development. Although [3H]polyuridylic acid binding sites were present in the generative and vegetative cells of maturing pollen grains, they almost completely disappeared from mature grains ready to germinate. During pollen germination, poly(A)+RNA formation was transient and was due to the activity of the generative nucleus, whereas the vegetative nucleus and the sperm cells failed to interact with the applied probe. In cultured anther segments, moderate amounts of poly(A)+RNA were detected in the uninucleate, nonvacuolate, embryogenically determined pollen grains. Poly(A)+RNA accumulation in these grains was sensitive to actinomycin D, suggesting that it represents newly transcribed mRNA. After the first haploid mitosis in the embryogenically determined pollen grains, only those grains in which the generative nucleus alone or along with the vegetative nucleus accumulated poly(A)+RNA in the surrounding cytoplasm were found to divide in the embryogenic pathway. Overall, the results suggest that, in contrast to normal gametophytic development, embryogenic development in the uninucleate pollen grains of cultured anther segments of H. niger is due to the transcriptional activation of an informational type of RNA. Subsequent divisions in the potentially embryogenic binucleate pollen grains appeared to be mediated by the continued synthesis of mRNA either in the generative nucleus or in both the generative and vegetative nuclei.
以[³H] - 聚尿苷酸为探针，通过原位杂交追踪了黑种草花粉粒在正常配子体发育以及花药切段培养诱导的胚性发育过程中含多聚腺苷酸的RNA（多聚腺苷酸 + RNA，poly(A)+RNA）的分布情况。在花粉粒发育的单核期，未检测到同位素结合。虽然在成熟花粉粒的生殖细胞和营养细胞中存在[³H]聚尿苷酸结合位点，但在即将萌发的成熟花粉粒中它们几乎完全消失。在花粉萌发过程中，多聚腺苷酸 + RNA的形成是短暂的，且是由生殖核的活性引起的，而营养核和精细胞未能与所应用的探针相互作用。在培养的花药切段中，在单核、无液泡、已确定具有胚性的花粉粒中检测到适量的多聚腺苷酸 + RNA。这些花粉粒中多聚腺苷酸 + RNA的积累对放线菌素D敏感，这表明它代表新转录的mRNA。在已确定具有胚性的花粉粒进行第一次单倍体有丝分裂后，仅发现那些生殖核单独或与营养核一起在周围细胞质中积累多聚腺苷酸 + RNA的花粉粒沿着胚性途径分裂。总体而言，结果表明，与正常配子体发育不同，黑种草培养花药切段中单核花粉粒的胚性发育是由于一种信息型RNA的转录激活。潜在胚性的二核花粉粒随后的分裂似乎是由生殖核或生殖核与营养核中mRNA的持续合成介导的。
