Identification and suppression of the p‐ coumaroyl CoA:hydroxycinnamyl alcohol transferase in Zea mays L.

Summary Grasses, such as Zea mays L. (maize), contain relatively high levels of p ‐ coumarates ( p CA ) within their cell walls. Incorporation of p CA into cell walls is believed to be due to a hydroxycinnamyl transferase that couples p CA to monolignols. To understand the role of p CA in maize development, the p ‐ coumaroyl CoA:hydroxycinnamyl alcohol transferase ( p CAT ) was isolated and purified from maize stems. Purified p CAT was subjected to partial trypsin digestion, and peptides were sequenced by tandem mass spectrometry. TBLASTN analysis of the acquired peptide sequences identified a single full‐length maize cDNA clone encoding all the peptide sequences obtained from the purified enzyme. The cDNA clone was obtained and used to generate an RNAi construct for suppressing p CAT expression in maize. Here we describe the effects of suppression of p CAT in maize. Primary screening of transgenic maize seedling leaves using a new rapid analytical platform was used to identify plants with decreased amounts of p CA . Using this screening method, mature leaves from fully developed plants were analyzed, confirming reduced p CA levels throughout plant development. Complete analysis of isolated cell walls from mature transgenic stems and leaves revealed that lignin levels did not change, but p CA levels decreased and the lignin composition was altered. Transgenic plants with the lowest levels of p CA had decreased levels of syringyl units in the lignin. Thus, altering the levels of p CAT expression in maize leads to altered lignin composition, but does not appear to alter the total amount of lignin present in the cell walls.