POPULATION CYTOGENETIC STUDIES CONFIRM X-Y MECHANISM IN ISOETES PANTII ( ISOETACEAE : PTERIDOPHYTA)

The evolution of the X-Y chromosome system has been revealed by chromosomal surveys of Isoetes species in ponds in and around Narsinghgarh, Central India. Because Isoetes pantii Goswami and Arya is a natural hybrid, it still has various chromosome numbers. However, plants with 2n=36,39, and 2n=48 always have heterosporous microsporangia bearing very aberrant megaspores of huge evolutionary significance. The emergence of the sex chromosomal mechanism appears to coincide with the evolution of heterospory within the microsporangia, a trait found nowhere else in the world. The emphasis is placed on resemblances of several genomic DNA sequences of I pantii to a few human Y chromosomal sequences, based on previous and current experimental procedures by DNA finger printing. Brief comments on recent discoveries of human Y chromosome MSY region DNA sequences in a bryophyte, Marchantia polymopha, and several other plants by various authors have also been discussed, with the goal of demonstrating that our hypothesis advanced in the 1990s that plants have some sequences from the human genome or vice versa, appears to be correct. All of these findings back up our earlier hypothesis, which was based on genomic studies as well as a computer search (DNA blasting) of a portion of Isoetes genomic DNA with human genomic data, that DNA sequences must have been continuously replicated and randomly distributed among evolving cells before the evolutionary lineage was bisected into plant and animal cells during the Pre Cambrian.

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