The reference gel (seeds aged for 0 d) for the total protein extract from poplar seeds aged for 0, 45 and 90 d.

<p>A total of 600 μg of proteins was extracted from poplar seeds, separated by 2-D gel as described in Materials and methods, and visualized with CBB. The protein spots accumulated differentially in different treatments are numbered and highlighted by circles and arrows. Their identities and properties are described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132509#pone.0132509.t001" target="_blank">Table 1</a>.