Q: What do plant fertilization, diurnal rhythms and hybrid vigour all have in common?

A: They are all connected by Epigenetics.

Presenting the first Annals of Botany Special Seminar* at the Plant Sciences Department at Oxford University on March 31st, Professor Jeff Chen (University of Texas) explained how his interest in polyploidy (the possession of more than the usual diploid sets of chromosomes) had led him to an understanding of hybrid vigour – where crosses between different plant lines can produce plants with yields greater than either parent and perhaps the most important challenge of modern plant breeding.

Some time ago Jeff realized that the different chromosome sets of polyploids somehow communicated with each other, and by entering the new and complex world of epigenetics – where modification of chromatin proteins and non-sequence-changing chemical alterations to the DNA can result in heritable traits – he was able to show that this was carried out via populations of small, non-coding RNA molecules. He showed the audience how, through a series of experiments using Arabidopsis polyploids and hybrids, his group had discovered that epigenetic systems regulate the level and rhythm of the expression of genes involved in photosynthesis and starch metabolism.

In these high-performing polyploids and hybrids, these genes were expressed at high levels during the day with several-fold increases over their parents. When, and precisely how, these expression patterns are set up will clearly require more research, but quoting unpublished work from his laboratory Jeff indicated that ‘relationships’ established between genomes during fertilisation by small RNA populations were important in determining which genes in which genomes were expressed in early development.

Jeff Chen is the D.J. Sibly Centenniel Professor in Plant Molecular Genetics in Texas, and currently holds a Fulbright Visiting Fellowship in Professor Sir David Baulcombe’s group at the Department of Plant Sciences, Cambridge University.

* Annals of Botany Special Seminars – a series of seminars run by Annals of Botany Editors that fund eminent researchers in plant sciences to give talks at their universities and Institutes. [↩]

Lab webpage: http://polyploidy.biosci.utexas.edu/

Key paper: Ni, Z., Kim, E., Ha, M., Lackey, E., Liu, J., Zhang, Y., Sun, Q., and Chen, Z. J. (2009) Altered circadian rhythms regulate growth vigour in hybrids and allopolyploids. Nature 457: 327-331 doi:10.1038/nature07523 (Mendeley)

Review: Chen, Z. J. (2010) Molecular mechanisms of polyploidy and hybrid vigor. Trends in Plant Science 15: 57-71. doi:10.1016/j.tplants.2009.12.003 (Mendeley)

Relevant AoB Reviews on epigenetics

(i) Grant-Downton, R. and Dickinson, H.G. (2005) Epigenetics and its implications in plant biology. 1. The epigenetic network in plants. Annals of Botany 96: 1143-1164. doi:10.1093/aob/mci273 (Mendeley)

(ii) Grant-Downton, R. and Dickinson, H.G. (2006) Epigenetics and its implications in plant biology; The ‘epigenetic epiphany’. 2. epigenetics, evolution and beyond. Annals of Botany 97: 11-27. doi:10.1093/aob/mcj001 (Mendeley)