Proline accumulation and related gene expression during spring regrowth in three rosaceae species

Abstract

Proline (Pro), one of amino acids, not only acts as an osmoprotectant but also is involved in plant developmental processes. We previously revealed that Pro levels increased in peach (Prunus persica) shoots during dehardening in response to warmer temperatures during spring or in controlled laboratory conditions. Our subsequent work suggested that such Pro accumulation is associated with the resumption of growth in eco-dormant shoots and mediated via the ornithine pathway in peach. The present study was conducted to explore whether the aforementioned Pro accumulation response also occurs in other species of the Rosaceae family. Our data indicate that the Pro content of peach and plum (P. salicina) shoots increased during the spring regrowth and were highly similar between these two related species. Whereas the ornithine-δ-aminotransferase (OAT) gene expression dynamics in peach were correlated with Pro accumulation pattern and with pyrroline-5-carboxylate reductase (P5CR) gene expression, OAT expression was not correlated with the Pro content in plum. For apple (Malus domestica), while the absolute amounts of Pro content differed from those of the two Prunus species, this species accumulated Pro during the spring warming/regrowth. These results suggest that Pro accumulation in response to higher temperatures during the spring regrowth is a more general phenomenon across Rosaceae fruit trees, and although peach shoots may accumulate Pro via the ornithine pathway during spring regrowth, there was no evidence for this in plum and apple.