Differential expression levels of <i>ZmUBC</i> genes following NaCl, PEG 6000, and 4°C treatment.

<p>The X-axis indicates time course/treatment and the Y-axes are scales of relative expression levels. The maize <i>actin</i> gene was used as internal control. The presented data are representative of three independent experiments.</p

Phylogenetic relationship of various ZmE2s.

<p>The ML tree includes 75 UBC proteins from <i>Zea mays</i>, 15 from <i>Saccharomyces cerevisiae</i>, and 48 from <i>Arabidopsis thaliana</i>. The tree shows 15 phylogenetic subgroups depicted in various colors to distinguish diversification of subfamilies into clusters.</p

Chromosomal and gene duplication events involving <i>ZmUBC</i> genes.

<p>The chromosomal position of each UBC-encoding gene was mapped to the maize genome. The chromosomal number is indicated at the top of each chromosome. The number below represented the number of UBC-encoding genes in each chromosome. The segmental duplication genes are connected by a blue straight line. The tandemly duplicated genes are linked by a red straight line. Chromosomal distances are in Mbp.</p

The information of ZmE2 gene family.

<p>The information of ZmE2 gene family.</p

Tissue-specific expression of <i>ZmUBC</i> genes.

<p>(A) Semi-quantitative RT-PCR analysis of <i>ZmUBC</i> genes. (B) RT-qPCR analysis of representative <i>ZmUBC</i> genes. The letter R above the column of the expression data refers to root, St represents stem, L indicates leaf, T refers to tassel, Ys indicates young seed, and Si represents silk.</p

The architecture of conserved protein motifs and intron pattern of ZmE2s.

<p>(A) Architecture of conserved protein motifs of UBC proteins. (B) The gene structure is presented by blue exon(s) and spaces between the blue box corresponding to intron (s). The sizes of the exons and intron can be estimated using the horizontal lines.</p

Phylogenetic tree of ubiquitin-conjugating (UBC) domains from <i>Carica papaya</i>, <i>Arabidopsis</i>, <i>Solanum lycopersicum</i>, and <i>Saccharomyces cerevisiae</i>.

<p>The neighbor-joining tree includes 34 UBC proteins from papaya (squares), 15 from <i>S</i>. <i>cerevisiae</i> (rhombi), 48 from <i>A</i>. <i>thaliana</i> (circles), and 52 from <i>S</i>. <i>lycopersicum</i> (triangles). The different colors indicate different CpUBC subgroups.</p

Structure of CpUBC genes.

<p>Untranslated 5′ and 3′ regions, exons, and introns are indicated by red, blue, and gray, respectively. The scale bar represents 1000 bp.</p

The information of <i>CpUBC</i> gene family.

<p>The information of <i>CpUBC</i> gene family.</p