TRNT1 and infection: In addition, considering that only FCS showed significantly heterosis for defense (Fig. 1a, f, g and Supplementary Fig. 12d) and CCA1 showed above-high parent expression pattern only in FCS hybrids at 21 hpi that occurred specifically upon pathogen infection (Fig. 1d, e and Supplementary Fig. 2), we speculated that CCA1 may confer heterosis for defense before the dawn of first infection day (21 hpi), the time that precisely precedes the peak of expression of SA biosynthetic genes and the burst of SA (24 hpi).