<i>LEAFY COTYLEDON1</i>, a Key Regulator of Seed Development, Is Expressed in Vegetative and Sexual Propagules of <i>Selaginella moellendorffii</i>

<div><p>LEAFY COTYLEDON1 (LEC1) is a central regulator of seed development that plays a key role in controlling the maturation phase during which storage macromolecules accumulate and the embryo becomes tolerant of desiccation. We queried the genomes of seedless plants and identified a LEC1 homolog in the lycophyte, <i>Selaginella</i><i>moellendorffii</i>, but not in the bryophyte, <i>Physcomitrella</i><i>patens</i>. Genetic suppression experiments indicated that <i>Selaginella LEC1</i> is the functional ortholog of <i>Arabidopsis</i><i> LEC1</i>. Together, these results suggest that <i>LEC1</i> originated at least 30 million years before the first seed plants appeared in the fossil record. The accumulation of <i>Selaginella LEC1</i> RNA primarily in sexual and asexual reproductive structures suggests its involvement in cellular processes similar to those that occur during the maturation phase of seed development.</p> </div

Lipid storage in bulbils.

<p>Vibratome-cut sections were stained with Sudan Black B to identify cells with neutral lipids. (A) Section through an <i>Arabidopsis</i> leaf with a low storage lipid content. (B) Stem and leaf section from <i>S</i><i>. moellendorffii</i>. (C) Section through a pumpkin oilseed with high storage lipid content. (D) <i>S</i><i>. moellendorffii</i> bulbil section. Stained lipids appears as dark blue or black. Air bubbles in A and B (arrows) appear dark and do not indicate staining. The images are representative of material from at least three different plants.</p

Vegetative and reproductive propagules of <i>S</i><i>. moellendorffii</i>.

<p>(A) Strobilus with basal microphylls removed to reveal axillary sporangia. (B) Mature, dormant bulbil. (C) Mature bulbil showing new shoot and root growth from apical and angle meristems respectively. (D) Longitudinal section of dormant bulbil stained with toluidine blue. showing the shoot apex and enlarged cells in the main body of the bulbil.</p

Phylogenetic tree based on the B domains of HAP3 subunits from yeast, <i>Arabidopsis</i>, <i>S.</i> moellendorffii, and <i>P</i><i>. patens</i>.

<p>Nodes with bootstrap values below 50 were collapsed.</p

<i>SmLEC1</i> is expressed in vegetative and reproductive propagules.

<p>qRT-PCR survey of <i>SmLEC1</i> mRNA levels in various <i>S</i><i>. moellendorffii</i> organs. No apices are shoot samples with growing tip removed to avoid sampling incipient propagules. Relative quantification of RNA levels was calculated using ubiquitin as a control. Error bars indicate standard deviations. The following comparisons were determined to be significantly different (p < 0.05): a vs c, b vs c, and a vs d.</p