The Mechanism Research Of Fast-growing Culms Of Phyllostachys Heterocycla

Moso bamboo is the most important bamboo species and the third most important plant species for timber production in China. It is a large woody bamboo with the highest ecological, economical, and cultural values among all bamboos in Asia and accounts for 5 billion US dollars of annual forest production in China.The growth of bamboo is very fast. In natural conditions, culms of developing Moso bamboo, Phyllostachys heterocycla, 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 within a complete development period was analyzed using histological section, enzyme-linked immunoassay, 2-DE combined with mass spectrometry identification and western blot. The main results are as followed: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 lignification was appeared at fibrous tissue of basal internode in G7 stage.The four major endogenous hormones, indole acetic acid (IAA), gibberellic acid (GA₃), zeatin riboside (ZR) and abscisic acid (ABA) appeared to strongly influence the internode development. The changes of four endogenous hormones all displayed a fluctuation during the development, but their peaks were out of synchronism. Cell division was significantly positively correlated with ZR concentration while cell elongation was significantly negatively correlated with ABA concentration. Cell elongation was significantly positively correlated with the ratio between promoting hormones (IAA, GA₃ and ZR) concentration and inhibitory hormone (ABA) concentration. These ratios had two peaks (G4 and G7). From histological observation result, the initially significant cell elongation occured at basal internode of G4. In G7, the significant cell elongation of middle internode and the initially lignification was appeared. So, we thought that hormonal equilibrium regulate the elongation and maturation of culm. Based on the above mentioned, G4 and G7 were defined as developmental-specific stage, which were combined with G1 and G9 for next analysis.According to the results histological section and enzyme-linked immunoassay, tissue samples of four stages were collected at nine different developmental stages from the basal, middle or top internodes and were analyzed separately by two dimensional electrophoresis. A total of 213 differentially expressed proteins included 189 unique proteins were identified by MALDI-TOF/TOF MS, of which 88 proteins were related to metabolism and energy and the remaining to cell growth, transcription, protein synthesis, protein sorting, transport, cell structure, signal transduction and disease/defense.Among the 213 differentially expressed proteins, 9 proteins (8 unique proteins) for which a significant difference in abundance only appeared among different developing internodes in the same developmental stage; while 175 proteins (155 unique proteins) for which difference in abundance only appeared among the different developmental stages in the same internode. In addition, 29 other proteins (26 unique proteins) for which significant difference in abundance appeared at both among different developmental internodes and among different developmental stages. These data suggest that both stage-specific and internode-specific proteins influence the developmental variations and that the majority of variations resulted from the stage-specific differences.Hierarchical clustering revealed that about 64% of these proteins were downregulated during development. Developmental stage-specific and internode-specific protein expression patterns were identified. Protein abundance was mainly regulated temporally and to some extent spatially. Many metabolic pathways were involved in differential expression, which include sucrose degradation, synthesis of pyruvate, glyoxylae cycle, TCA cycle, pentose-phosphate pathway, shikimic acid pathway, fatty acid oxidation, and synthesis of amino acid. Also, many elongation factors, transcript factors, eukaryotic initial factors and stress proteins were differentially expressed. This indicate the energy foundation and metabolic direction of fast-growing of culm.Results indicate that during development, energy was mainly derived from sucrose degradation, as photosynthetic capacity was poor. The fructokinase play an important role in energy production. 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.