Abstract
Arabidopsis L1L is a B subunit of the hetero trimeric CCAAT binding factor NF-Y, most closely related to LEC1. L1L is specifically expressed during seed development and requires the key regulators of seed development, LEC1 and FUS3 for its expression. L1L can activate the promoter of a seed storage protein CRC gene in T87 cells when co-expressed with an NF-YC subunit, HAP5B and ABRE-binding factors, bZIP12/bZIP67. We showed here evidence for complex formation between L1L-HAP5B and bZIP67. We also demonstrated that the expression of a seed specific sucrose synthase gene, SUS2 was reduced in a l1l mutant and that L1L-HAP5B and bZIP67 could activate its promoter like the CRC promoter. The transcriptional activation by these factors required ABREs but not CCAAT motifs and could not be enhanced by NF-YA subunits. These observations suggested that the L1L-HAP5B hetero dimer activates transcription by acting on ABREs through the interaction with bZIP12/bZIP67.
