FCS (F1 of Col-0 X Sei-0) shows a lower expression level of CCA1 at 6 hpi (hour post pst DC3000 infection), while shows a higher expression level of CCA1 at 21 hpi. This allows that FCS contains heterosis for both growth and disease resistance (enhanced SA biosynthesis).
By constructing hybrids of cca1 mutant in the isogenic background, the contribution of CCA1 was determined.
The author believed rhythmic histone modifications (H3Ac, H3K4me) contribute to this precise control of CCA1 expression.
Notes:
1) Living condition of plants: 12 hr light/12 hr dark;
2) 21 days-old plant used for bacterial infection;
3) ~1000 bp upstream TSS of DEGs used for cis analysis;
4) GO: http://bioinfo.cau.edu.cn/agriGO/
5) 1, 2, and 3 dpi samples used for RNA seq (not clear when is the exact time for sample collection)