What is the importance of MMC undergoing meiosis?

Megasporogenesis and Gametophyte Development

• In gymnosperms and most flowering plants, only one of the four megaspores formed during meiosis is functional at maturity, while the other three degenerate.
• The functional megaspore undergoes mitotic divisions to develop into the female gametophyte (embryo sac), which eventually produces a single egg cell.

Gametophyte Formation

• In flowering plants, particularly in the Polygonum type (the most common type of megagametophyte development), the functional megaspore undergoes three mitotic divisions.
• This results in a seven-celled structure: one egg cell, two synergids, three antipodal cells, and a central cell.
• The central cell contains two nuclei, which later fuse to form a diploid nucleus.

Double Fertilisation

• Flowering plants exhibit double fertilisation, where two male gametes (sperm cells) participate in fertilisation:
  • One sperm fertilises the egg cell, forming the zygote (embryo).
  • The other sperm fertilises the central cell, forming the endosperm, which nourishes the developing embryo.

Meiosis and Megasporogenesis

• Meiosis is the type of cell division that produces four haploid daughter cells, each with half the number of chromosomes of the parent cell.
• In plants, megasporogenesis is the process by which megaspores are formed from the megaspore mother cell (MMC or megasporocyte) inside the ovule of the ovary.
• The MMC is diploid and, through meiotic division, produces four haploid megaspores. Typically, only one megaspore remains functional, while the others degenerate.
• The functional megaspore develops into the female gametophyte (embryo sac).

Note

In Arabidopsis, actin-related proteins regulate meiotic gene expression in the megaspore mother cell, influencing female meiosis. One key gene involved is Dmc1, which plays a role in meiotic recombination repair through strand-exchange processes.