Temporal and Spatial Profiling of Internode Elongation-Associated Protein Expression in Rapidly Growing Culms of Bamboo

In natural conditions, culms of developing Moso bamboo, <i>Phyllostachys heterocycla</i> var. <i>pubescens</i>, reach their final height of more than ten meters within a short period of two to four months. To study this phenomenon, bamboo culm material collected from different developmental stages and internodes was analyzed. Histological observations indicated that the development of culm was dominated by cell division in the initial stages and by cell elongation in the middle and late stages. Development, maturation, and aging in different regions of the culm were studied systematically from the basal to the top internode. The four major endogenous hormones, indole acetic acid, gibberellic acid, zeatin riboside, and abscisic acid appeared to strongly influence the cell elongation phase. A total of 258 spots were differentially expressed in culm development. Of these, 213 spots were identified by MALDI-TOF/TOF MS and were involved in many physiological and metabolic processes including carbohydrate metabolism, cell division, cell expansion, protein synthesis, amino acid metabolism and redox homeostasis. These proteins with different expression patterns constructed an ingenious network to regulate the culm development. Developmental stage-specific and internode-specific protein expression patterns were identified. Protein abundance was regulated temporally and to some extent spatially, and the sequential development from base to apex of bamboo culm was implemented by temporal and spatial expression of enzymes. Results indicate that during development energy was mainly derived from sucrose degradation, as photosynthetic capacity was poor. The regulation of anaerobic and aerobic modes of respiration appeared to play an important role in energy generation. This is the first report on proteomic profiling in bamboo and helps in understanding the regulatory processes in developing culms