Transcriptome and proteome analysis suggest enhanced photosynthesis in tetraploid Liriodendron sino-americanum

Polyploidy generally provides an advantage in phenotypic variation and growth vigor. However, the underlying mechanisms remain poorly understood. The tetraploid Liriodendron sino-americanum (Liriodendron × sinoamericanum P.C Yieh ex C.B. Shang & Zhang R.Wang) exhibits altered morphology compared with its diploid counterpart, including larger, thicker and deeper green leaves, bigger stomata, thicker stems and increased tree height. Such characteristics can be useful in ornamental and industrial applications. To elucidate the molecular mechanisms behind this variation, we performed a comparative transcriptome and proteome analysis. Our transcriptome data indicated that some photosynthesis genes and pathways were differentially altered and enriched in tetraploid L. sino-americanum, mainly related to F-type ATPase, the cytochrome b6/f complex, photosynthetic electron transport, the light harvesting chlorophyll protein complexes, and photosystem I and II. Most of the differentially expressed proteins we could identify are also involved in photosynthesis. Our physiological results showed that tetraploids have an enhanced photosynthetic capacity, concomitant with great levels of sugar and starch in leaves. This suggests that tetraploid L. sino-americanum might experience comprehensive transcriptome reprogramming of genes related to photosynthesis. This study has especially emphasized molecular changes involved in photosynthesis that accompany polyploidy, and provides a possible explanation for the altered phenotype of polyploidy plants in comparison with their diploid form.