Which is the best source to study the subject of chloroplast formation in the zygote forming algae (single or multi celled species). Is the mechanism analogous to that of proplastids in plant zygotes?
In multiplication by cell division in microalgae or the vegetative cells of macroalgae it is clear, each chloroplast keeps pace with the dividing nucleus, dividing in synchronization and each daughter cell receives a copy of the original chloroplast.
But what about the fusion of gametes to form a zygote? What is the fate of the chloroplasts they carry? I reckon that the zygote rearranges everything and creates new proplastids that carry the original chloroplast DNA. The zygote proplastids then develop in new chloroplasts in the produced cells.
I think this topic is not covered clearly in textbooks and any advice is welcomed.
Professor George N Hotos
Non-Mendelian inheritance of organellar genome is the norm in almost all sexual eukaryotic algae and in most cases the inheritance of chloroplast is uniparental because irrespective of the fusion of contents from two parental gametes, one of the chloroplast DNA disintegrates after couple of hours. The rearrangement you quoted happens or commences with the methylation of cpDNA during zygote differentiation, thus heralding zygote maturation.
With regards,
Dr. Abhishek Mukherjee
Very consice explanation Dr Mukherjee, thank you. I want to clarify further the nature of chloroplast developing entity in the zygote. Is it intact from only one "parent" or starts from a proplastide-like body? Any detailed textbook or paper in this subject?
My best regards
George Hotos
Braten, T. (1971). The ultrastructure of fertilization and zygote formation in the green alga Ulva mutabilis Foyn. J. Cell Sci, 9, 621-635.
da Silva, J., & Drysdale, V. L. (2018). Isogamy in large and complex volvocine algae is consistent with the gamete competition theory of the evolution of anisogamy. Proceedings of the Royal Society B, 285(1890), 20181954.
Thank you very much dear Asiel. I'll study your proposed papers.
George
Prof. George N. Hotos
I apologize for the unintentional delay in my reply to your response. In your defense I'd say it has to start like a proplastid-like organelle since during the formation neither photosystems are functional which should render the future plastid merely rudimentary during zygote formation. The following links should aid you in your research:
1. Chloroplast Biogenesis: Control of Plastid Development, Protein Import, Division and Inheritance.
2. ULTRASTRUCTURE OF PLASTID INHERITANCE: GREEN ALGAE TO ANGIOSPERMS.
3. The fate of chloroplast DNA during cell fusion, zygote maturation and zygote germination in Chlamydomonas reinhardi as revealed by DAPI staining.
4. Disintegration of Chloroplasts during Zygote Maturation in Closterium ehrenbergii (Zygnematales, Chlorophyta).
With regards,
Dr. Abhishek Mukherjee
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