Leaf maturation, as an important event in leaf development, is closely related to photosynthesis efficiency and regulated by various proteins. Data from 2D gel analysis indicated that some proteins were up-regulated and others Fig. 4 The expression patterns of Ib-RCA genes in a photoperiod. a Expression patterns of the Ib-RCA genes by relative quantitative real-time PCR as shown in graphs. RNA samples were collected at 2 h interval from 0 to 22 h. b Expression patterns of the Ib-RCA genes by semi-quantitative PCR as shown in gels. The bactin was used as a control. Inside graph is the change of temperature in a photoperiod. Data (mean ± SE) are typical results from three independent experiments performed were down-regulated in young and mature leaves. Due to lack of the complete genomic information of sweet potato, it was difficult to identify differentially expressed proteins by MALDI-TOF-TOF-MS. In order to obtain this information, the NCBI GreenPlants database and the transcriptomic database of sweet potato were used for homology analysis. Meanwhile, the **data** from semi-quantitative RT-PCR demonstrated that at both transcript and protein levels, these proteins had the same tendency of upor down-regulation although the fold of increase or decrease was different (Figs. 1, 2). Because it is a complex process from mRNA to protein, both post-transcriptional and post-translational events could have caused the differences between mRNA and protein levels [32,33]. Among the identified proteins, nearly 50 % were associated with photosynthesis in the process of leaf maturation, and most were up-regulated. This result suggests that the improvement of photosynthetic system was a key event in the process of leaf maturation, and the leaf goes through a transition from heterotrophic nutrition to autotrophic nutrition.