Ecogenomics of cleistogamous and chasmogamous flowering: genome-wide gene expression patterns from cross-species microarray analysis in Cardamine kokaiensis (Brassicaceae)

Authors


Correspondence author. Department of Biology, Graduate School of Sciences, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. E-mail: smoriscb@mbox.nc.kyushu-u.ac.jp

Summary

  • 1Cleistogamy is a mating system found in approximately 300 species of flowering plants. Cleistogamous plants produce closed (cleistogamous, CL) flowers that require obligate self-pollination and open (chasmogamous, CH) flowers that allow for outcross-pollination. CL and CH flowers are induced by various environmental factors; this appears to be an adaptive mating strategy in unpredictable environments.
  • 2We examined the molecular basis of CL and CH flowering in Cardamine kokaiensis, which is closely related to the model flowering plant Arabidopsis thaliana. CL and CH flowering should be regulated by gene expression that is dependent on environmental conditions. By elucidating the molecular basis of CL and CH flowering, we can determine the changes in gene regulatory networks involved in the transition from CH to CL flowering. Furthermore, these results may help clarify the molecular evolutionary mechanisms leading to cleistogamy.
  • 3We regulated CL and CH flowering of C. kokaiensis using chilling treatments in a growth chamber. In a control treatment without chilling, C. kokaiensis produced CH and intermediate (INT) flowers. Long chilling of seedlings led to INT flowers, while long chilling of seeds induced the formation of CL flowers. Chilling seeds, and to a lesser extent of seedlings, induced early flowering and small plant size at flowering.
  • 4We also conducted a cross-species microarray analysis to compare gene expression patterns between CL and CH flowers using genomic DNA-based probe-selection strategy in an A. thaliana microarray. In this result, 69 genes, including genes related to floral development, auxin, flowering time, cold-stress, and drought-stress, were differentially expressed between CL and CH flowers.
  • 5Synthesis. This is the first report on the molecular basis of cleistogamy. We hypothesize that the interaction between the genetic network of the chilling response and that of floral development has been important in the evolution of cleistogamy in C. kokaiensis. Our results help to clarify the molecular basis for the evolution of plant mating systems that depend on environmental conditions.

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