| Scope and Method of Study. Shortleaf pine sprouts prolifically after disturbance such as fire. Much attention has been paid to its restoration due to its increasingly declining population. Shortleaf pine's strong sprouting ability has huge potential in promoting its regeneration. However, little is known about its sprouting mechanism at the molecular level. A microarray experiment was designed to study genes responsible for this sprouting ability.Findings and Conclusions. In this study, one year old shortleaf pine and loblolly pine seedlings are top-killed, and tissues collected just before sprouting were used. As in the natural environment, shortleaf pine showed extraordinary strong sprouting ability and large amounts of sprouts were seen two days after top-killing. However, on loblolly pine only a few sprouts were seen one week after top-killing. By microarray gene profiling with about 2400 cDNA clones obtained from suppression subtractive hybridization, 139 differentially expressed genes were found to be associated with sprouting, including genes functioning in reserve (carbohydrates and fatty acid) mobilization, transcriptional regulation, stress response, plant development, signal transduction and hormone regulation. 130 differentially expressed genes were found to be responsible for the dormancy release of axillary buds of shortleaf pine after top-killing. In contrast, only 32 differentially expressed genes were detected for loblolly pine. Shortleaf pine responds actively to top-killing at the molecular level. As reported for dormancy release of buds of other perennial plants, oxidative stress might be the major factor in dormancy release of axillary buds of shortleaf pine. It is apparent that cross talking between plant hormones (especially gibberellins, ethylene and auxins), carbohydrates, and other players of signal transduction work cooperatively to promote sprouting of shortleaf pine after top-killing. |
