Vegetative storage proteins in the tropical tree Swietenia macrophylla: seasonal fluctuation in relation to a fundamental role in the regulation of tree growth

Abstract

The protein-storing cells in Swietenia macrophylla King were investigated. They were found to be of the Populus type, i.e., ordinary parenchyma cells containing both vacuole protein inclusion and starch grains. Vegetative storage proteins with molecular masses of 18 and 21 kDa were separated by SDS–PAGE (sodium dodecyl sulfate – polyacrylamide gel electrophoresis). Immunoblotting with the 21-kDa protein antiserum showed that the 18- and 21-kDa proteins shared common epitopes. The 21-kDa protein and presumably the 18-kDa protein were demonstrated by immunogold labeling to be the main components of the vacuole protein inclusion of the protein-storing cells. At the late stage of an annual growth cycle, vegetative storage proteins were found in the branchlets, trunk, large roots, and small roots. They were stored in large amounts in the secondary phloem of these organs and also in the secondary xylem of the terminal branchlets and small roots. In a new growth cycle, the consumption of the previously accumulated vegetative storage proteins began in the terminal branchlets of the last growth cycle. The vegetative storage proteins in the branchlets were exhausted completely when the new shoot leaves matured, while the storage proteins in the trunk and large roots had no detectable changes in abundance. On the other hand, the tree started to accumulate the two proteins in the stem of the new shoots as early as 1 week after the new shoot leaves matured. These results suggested that the previously accumulated vegetative storage proteins were used for new shoot growth and cambial activity in preference to the newly assimilated nitrogen and that vegetative storage proteins existed in considerable amounts in the stems throughout an annual growth cycle. This seasonal fluctuating pattern of vegetative storage proteins in the whole tree may be an important mechanism by which the tree regulates its growth.Key words: vegetative storage proteins, nitrogen metabolism, Populus-type of protein-storing cells, tropical hardwoods, Swietenia macrophylla King.

A protein extraction method compatible with proteomic analysis for the euhalophyte Salicornia europaea

“…The protein extraction buffer was optimized from the published ones [32,33]. In short, 1 g of frozen lyophilized tissue powders was resuspended in 3 mL ice-cold extraction buffer of 100 mM Tris (pH 8.0) containing 100 mM EDTA, 50 mM borax, 50 mM vitamin C, 1% PVPP w/v, 1% Triton X-100 v/v, 2% b-mercaptoethanol v/v and 30% sucrose w/v.…”

Fluctuation of Vegetative Storage Proteins in the Seedlings of Swietenia macrophylla, Analogous to the Seasonal Changes of Those in the Shoot of the Adult Tree

“…However, we recently discovered a basic fluctuation pattern of vegetative storage proteins in both the tropical tree S. macrophylla (Tian et al 2003) and the temperature tree Populus canadensis (Tian et al 2005). This pattern was characterized by the space-time differential expression of VSP gene and the space-time differential accumulation and mobilization of VSPs (Tian et al 2005).…”

“…This pattern was characterized by the space-time differential expression of VSP gene and the space-time differential accumulation and mobilization of VSPs (Tian et al 2005). The accumulation of VSPs did occur in the stem of new shoots as early as 1 week after the new shoot leaves matured in spring under conditions of high temperatures, long days and continuous growth (Tian et al 2003(Tian et al , 2005. So, the initiation of VSP accumulation had no close relationship with the external factors such as low temperatures and short days described above.…”

“…The external factors, such as low temperature and short days, have been emphasized as key signals in inducing VSP accumulation in trees (Causen and Apel 1991;Langheinrich and Tischner 1991;Coleman et al 1991Coleman et al , 1992Coleman and Chen 1993). Recently, we found that the seasonal fluctuation of VSPs was very similar between the tropical tree S. macrophylla and the temperate tree Populus canadensis, suggesting that this seasonal fluctuation pattern in the whole tree might be an important mechanism by which the trees regulated their growth (Tian et al 2003(Tian et al , 2005. Based on this seasonal pattern, the trees begin to accumulate VSPs under conditions of high temperatures and long days.…”

“…The 18-and 21-kDa proteins were identified to be VSPs in S. macrophylla adult trees (Tian et al 2003). In S. macrophylla seedlings, an 18-kDa and a 21-kDa protein were detected in the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profile of soluble proteins from the stem.…”