Few weeks ago, our LONG LAB gets a retreat at LONG LAKE Delton, MI. During the retreat, we presented our recent few months’ work; enjoyed our delicious food come from global, enjoyed the sunshine in the peaceful lake, and also the boating and swimming. However, the thing still keep in my mind is not the beautiful lake, not the peaceful forest, not the nice and warm bonfire, but the theory, or the hypotheses, from professor Bai, who is famous by his work at the organ development in plant.
The hypothesis from Bai is generally around the question, what is the sex? Is sex universally existed? How to define the sex in plant?
As we all know, that human being has two genders, male and female, which can generally be distinguished by the sex organs. However, sometimes, we will meet the problem, like the noted events happened on Erik Schinegger (http://en.wikipedia.org/wiki/Erik_Schinegger). Erika was the world champion of women’s downhill skier in 1966, however, the medical test by the International Olympic Committee (IOC) show that Erika should be the Erik, which means that Erik is an intersexual person. Checking the sporting history, you will found several such cases, like Santhi Soundarajan (http://en.wikipedia.org/wiki/Santhi_Soundarajan) and Renée Richards (http://en.wikipedia.org/wiki/Ren%C3%A9e_Richards). Now, we know that, sometime, God will play trickiness on some unlucky person, that they will own wrong chromosomes, XXY. Here, X and Y representative X chromosome and Y chromosome, which determining the human sex, if one person own the XX, then, she should be the female, if own the XY, he should be the male, while if it is XXY, then, the unlucky happens, that s/he should be the intersexual person.
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It is already a little complex on the human being, however, compare to the plant, it is just a piece of cake, at least, the human being have the clear entire chromosome that which will determine the sex, while in the plant, most of them doesn’t have an sex chromosome. As I know, Carica papaya (image was download from the internet) is in early evolutionary stage, it still keep the trace that how it generate its sex chromosome system , the paper was published in PNAS by Jianping Wang, Andrea R Gschwend and colleagues (Wang et al., 2012).And we also know that, the plant has variable system compare to the human. For papaya, it has |
both the pistillate plants, male plants and also monoecism, and sometimes, it will have male flowers on the pistillate plants. Generally, it’s really a complex filed that attracted a lot of interesting on it. However, the difficult not only presented on the sex part, but others. Professor Bai also asks the definition of the plant individual. What is an individual of the plant?
We all know that, some plants can only survival for one year called as annual grass like Oryza sativa (cultured rice); some can survival for several years are called perennial plants like Oryza officinalis (wild rice), however, and we also know that some plant can even exists for thousands years like Dracaena draco (http://en.wikipedia.org/wiki/Dracaena_draco), the interesting thing is that, if we move the annual grass plant to a suitable place, it can survive for more than one years (As I know one case happened in my previous lab is that one mutation line of rice survived for more than ten years, and never flowering). So, what are the start and the end of one life in plant? How can an individual have a life without an end? Based on these phenomenon, professor Bai give out a hypotheses (Shu-Nong Bai and Zhi-Hong Xu, 2013), (Bai & Xu, 2012)that maybe, in plant, we need to make a change on the point of view.
The plant, that living there looks like a tree or grass, is not an individual body, but a system, the system will change according to the environment, and the flowers generated from the system, is the individual body, generally, every flowers, whatever it is, pistillate flower, male flower or monoecism flower, is an individual body blocked something region in the chromosome related to the sex determination. And generally, the leaves along with the flower, they will wither in less than one year, then, we can make everything easier than previous, that every individual life in plant (follower) have less than one year life time, if they does not have an flower, then, there’s no individual there, it is just a system, and the next generation of the plant started after the seed become a suitable system that another flower is there. This hypothesis is far away to be the truth, but do give us a good and interesting view.
May be in one day, our human body, will become a system, which can survival for thousands years, and only produce our offspring when we have to.
Bai, S.-N., & Xu, Z.-H. (2012). Bird-nest puzzle: can the study of unisexual flowers such as cucumber solve the problem of plant sex determination? Protoplasma, 249 Suppl , S119–23. doi:10.1007/s00709-012-0396-4
Bai SN, Xu ZH, (2013) .Unisexual Cucumber Flowers, Sex and Sex Differentiation. In Kwang W. Jeon, editor: International Review of Cell and Molecular Biology, Vol. 304, Burlington: Academic Press, 2013, pp. 1-55. ISBN: 978-0-12-407696-9
Wang, J., Na, J.-K., Yu, Q., Gschwend, A. R., Han, J., Zeng, F., … Ming, R. (2012). Sequencing papaya X and Yh chromosomes reveals molecular basis of incipient sex chromosome evolution. Proceedings of the National Academy of Sciences of the United States of America, 109(34), 13710–5. doi:10.1073/pnas.1207833109