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To gain insight into possible relationships in gene coexpression and regulation, we
first identified the expression patterns for several TFs known to regulate the accumulation
of seed storage reserves (Figure 6). AGL15 (AGAMOUS-LIKE 15), GL2 (GLABRA2), LEC1, L1L, and WRI1 exhibited similar expression patterns with most genes encoding proteins involved in
FA biosynthesis (Figure 6A) whereas ABI3, EEL, and FUS3 all have similar expression profiles with genes encoding oleosins and SSPs (Figure
6B). Two repressors of seed maturation genes, ASIL1 (ARABIDOPSIS 6B-INTERACTING PROTEIN 1-LIKE 1) [69] and PICKLE (PKL) [70], were modestly expressed and exhibited a stable expression pattern throughout seed
maturation (Figure 6C). Surprisingly, LEC2, a TF gene known to regulate oil accumulation in leaves and somatic embryogenesis
[10,14,16], was barely detectable in these developing seeds. Although this result requires verification
with other molecular methods, it was previously reported that LEC2 might be only expressed during early embryo morphogenesis [15]. Additionally, based on phenotype descriptions of LEC1, LEC2 mutants in the Arabidopsis Information Resource (TAIR) [71], the accumulation of storage compounds in the mature lec2 mutant seeds is only slightly defective when compared to lec1 mutant seeds. Therefore, the role of LEC2 as a regulator in the synthesis of seed storage reserves during late stages of zygotic
embryo development might not be as important as currently thought. Likewise, ABI4 was also essentially unexpressed in these seed samples. The expression similarity
between genes encoding TFs and their target genes is suggestive of regulatory relationships.
Both LEC1 and WRI1 were clustered with most FA biosynthetic genes, while ABI5 was clustered with the majority of LATE-EMBRYOGENESIS ABUNDANT (LEA) genes (Figure 3 Cluster 3). LEC1 and WRI1 are known to regulate many FA biosynthetic genes [25-27], and ABI5 regulates a subset of LEAs [72].
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