Induction of reproductive organ-preferential histone genes by wounding or methyl jasmonate

A cDNA clone CaH2B, which is highly expressed in floral buds, was isolated from hot pepper plants (Capsicum annum) by the mRNA differential display me thod. Sequence analysis of CaH2B revealed that the clone contains an open r eading frame of 145 amino acid residues, which are 77% identical to a maize H2B histone. The CaH2B mRNA was barely detectable in roots, was more abund ant in anthers than in seedlings, and was expressed highest in floral buds and fruits. An in situ analysis of CaH2B in floral buds indicated that the transcript is highly present in the pollen and petals. Northern analysis of CaH4, a pepper H4 histone cDNA, which was obtained during the expressed se quence tag (EST) analysis of anther tissues, showed that the expression pat tern was very similar to that of CaH2B, although the expression level was s lightly different. Both histone genes were examined for inducibility by wou nding, methyl jasmonate (MJ), or phytohormones. CaH2B and CaH4 were induced by wounding, and maximally induced ca. 3 h after wound treatment both in v itro and in planta. Airborne MJ greatly induced the expression of the genes as well. The inducing effect by wounding was suppressed by MJ, suggesting that wounding and MJ might have different roles in signal transduction for the histone gene induction. Southern blot hybridization showed that both H2 B and H4 genes are comprised of multigene families in the hot pepper.