Abstract
Heterotrimeric Heme Activator Protein (HAP) family genes are involved in the regulation of flowering in plants. It is not clear how many HAP genes regulate heading date in rice. In this study, we identified 35 HAP genes, including seven newly identified genes, and performed gene duplication and candidate gene-based association analyses. Analyses showed that segmental duplication and tandem duplication are the main mechanisms of HAP gene duplication. Expression profiling and functional identification indicated that duplication probably diversifies the functions of HAP genes. A nucleotide diversity analysis revealed that 13 HAP genes underwent selection. A candidate gene-based association analysis detected four HAP genes related to heading date. An investigation of transgenic plants or mutants of 23 HAP genes confirmed that overexpression of at least four genes delayed heading date under long-day conditions, including the previously cloned Ghd8/OsHAP3H. Our results indicate that the large number of HAP genes in rice was mainly produced by gene duplication, and a few HAP genes function to regulate heading date. Selection of HAP genes is probably caused by their diverse functions rather than regulation of heading.
Highlights
The heterotrimeric Heme Activator Protein (HAP) complex is known as the CCAAT box factor (CBF) or nuclear factor Y (NF-Y) (Mantovani, 1999)
We identified four HAP family genes that were associated with heading date, based on a diverse germplasm collection
We tested the function of 18 HAP genes on heading date by overexpressing or silencing cDNAs from Nipponbare seedlings and nine mutants that were targeted at HAP genes
Summary
The heterotrimeric Heme Activator Protein (HAP) complex is known as the CCAAT box factor (CBF) or nuclear factor Y (NF-Y) (Mantovani, 1999). The HAP complex consists of three subunits: HAP2 (NF-YA; CBF-B), HAP3 (NF-YB; CBF-A), and HAP5 (NF-YC; CBF-C). This complex binds to CCAAT sequences in a promoter to control the expression of target genes (Gusmaroli et al, 2001; Kusnetsov et al, 1999). There is a single gene for each HAP subunit, while in plants, there are gene families encoding each subunit. Recent studies have revealed the function of members of the HAP family in multiple plant developmental processes. NFYA3 and NF-YA8 are functionally redundant genes that are required in the early embryogenesis of Arabidopsis (Fornari et al, 2013).
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