Arabidopsis NF‐YB subunits LEC1 and LEC1‐LIKE activate transcription by interacting with seed‐specific ABRE‐binding factors

Abstract

SUMMARYLEAFY COTYLEDON 1 (LEC1) plays vital roles in the regulation of seed maturation in Arabidopsis. LEC1 encodes a homolog of yeast HAP3 or mammalian NF-YB/CBF-A subunit of trimeric CCAAT binding factor (CBF). Among the nine paralogs of NF-YB in Arabidopsis, LEC1-LIKE (L1L) is most closely related to LEC1, and can complement the lec1 mutation when expressed under the control of the LEC1 promoter. Although the nature of the B3-type seed maturation regulators as transcription factors have been investigated, knowledge of the molecular action of LEC1 is limited. When co-expressed with NF-YC2 in the presence of ABA, we found that LEC1 or L1L, but not other NF-YBs, activated the promoter of CRUCIFERIN C (CRC), which encodes a seed storage protein. However, additional expression of an NF-YA subunit interfered with the activation. The LEC1/ L1L-[NF-YC2] activation depended on ABA-response elements present in the promoter, which led to the finding that LEC1/L1L-[NF-YC2] can strongly activate the CRC promoter in the absence of ABA when co-expressed with a seed-specific ABA-response element (ABRE)-binding factor, bZIP67. Functional coupling of LEC1/L1L-[AtNF-YC2] and bZIP67 was also observed in the regulation of sucrose synthase 2 (SUS2). Immunoprecipitation experiments revealed that L1L and bZIP67 formed a protein complex in vivo. These results demonstrate a novel plant-specific mechanism for NF-Y subunit function that enables LEC1 and L1L to regulate a defined developmental network.

Identification of Direct Targets of FUSCA3, a Key Regulator of Arabidopsis Seed Development

“…In addition, FUS3 directly associated with AGL15 and BBM, which, like LEC1 and L1L, can promote somatic embryogenesis. L1L has been reported to interact with bZIP67, the gene for which is also potentially regulated by FUS3, and these factors together control the expression of CRC (At4g28520) and SUS2 (At5g49190; Yamamoto et al, 2009). FUS3 also directly up-regulates LBD40, which may be a direct target of ABI3 and LEC2 (Braybrook et al, 2006) as well.…”

“…VAL1 (with the redundant VAL2) information is from Suzuki et al (2007). The double blue lines indicate protein interaction (ABI3-ABI5 [Nakamura et al, 2001] and L1L-bZIP67 [Yamamoto et al, 2009]). Regulation of AtEM1 and AtEM6 (Bensmihen et al, 2002), of ABI5 (Lopez-Molina et al, 2002, and of fatty acid biosynthesis genes (Maeo et al, 2009) is also shown.…”

Global analysis of gene activity duringArabidopsisseed development and identification of seed-specific transcription factors

“…Genetic studies with Arabidopsis have uncovered several genes that play major roles in seed development (9)(10)(11), including those that govern endosperm formation (12,13), embryo differentiation (14,15), and seed coat development (8). In addition, molecular studies with Arabidopsis and other plants have identified the ciscontrol regions of several genes active during seed development, particularly those encoding storage proteins, and the transcription factors (TFs) that play a role in their regulation (16)(17)(18)(19)(20)(21)(22). Nevertheless, the identities of most regulators of seed development and their direct targets are largely unknown.…”

The Evolutionary History of CBF Transcription Factors: Gene Duplication of CCAAT – Binding Factors NF-Y in Plants

“…Additionally, several groups have demonstrated that each of the three plant NF-Y proteins can substitute their yeast counterparts in gene expression assays (Edwards et al, 1998;Masiero et al, 2002;Ben-Naim et al, 2006;Siefers et al, 2009). These observations indicate that plant NF-Y subunits might act as general transcription factors, as in mammals (Yamamoto et al, 2009). Although a complete functional plant NF-Y complex has not yet been described, the individual subunits are known to be involved in a number of important physiological processes, such as specific developmental processes and response to environmental stimuli (Lotan et al, 1998;Kusnetsov et al, 1999;Miyoshi et al, 2003;Ben-Naim et al, 2006;Combier et al, 2006;Wenkel et al, 2006;Cai et al, 2007;Nelson et al, 2007;Warpeha et al, 2007;Siefers et al, 2009).…”