The inhibition of polyamine biosynthesis weakens the drought tolerance in white clover (<Emphasis Type="Italic">Trifolium repens</Emphasis>) associated with the alteration of extensive proteins

Changes of endogenous polyamine (PA) levels could be a key adaptive response to drought in plants. White clover pretreated with or without dicyclohexylamine (DCHA), an inhibitor of PA biosynthesis, was subjected to drought stress induced by 18% polyethylene glycol 6000 for 8 days in controlled growth chambers. Results showed that drought stress significantly increased endogenous PA content, whereas DCHA significantly decreased PA accumulation under drought stress. The attenuate PA biosynthesis was unfavorable for plant growth and drought tolerance, as reflected by significantly lower relative water content, relative growth rate, instantaneous water use efficiency, and cell membrane stability in leaves in response to drought. On the basis of proteomic analysis, the inhibition of PA synthesis decreased the accumulation of many key differentially expressed proteins including (1) ribosomal structure and biogenesis: elongation factor, ribosomal protein S10E, and 30S ribosomal protein; (2) amino acid transport and metabolism: cysteine synthase, delta-1-pyrroline-5-carboxylate synthetase, and glutamate decarboxylase; (3) carbohydrate metabolism and energy production: photosystem apoprotein, sucrose-phosphate synthase, phosphogluconate dehydrogenase, sucrose-phosphatase, NADH oxidoreductase, and ATP synthase; (4) antioxidant metabolism: catalase, peroxidase I, ascorbate peroxidase, and glutathione S-transferase; and (5) other biological processes: heat shock protein 70, heat shock protein 90, and calcium-dependent protein kinase associated with the decreased drought tolerance in white clover. These findings indicate that PAs play a critical role in the regulation of growth, ribosome, amino acid and energy metabolism, and antioxidant reactions in white clover under drought stress. Drought-induced increases in endogenous PAs could be one of key adaptive responses against drought stress in white clover.     

Ploidy Level and DNA Content of Erianthus arundinaceus as Determined by Flow Cytometry and the Association with Biological Characteristics

Erianthus arundinaceus is not only an important germplasm resource for sugarcane breeding but also a potential bioenergy plant. Making clear the distribution of the chromosome ploidy of wild E. arundinaceus in china is the premise of the research and utilization of this species. Therefore, the objectives of this study were to determine the ploidy level and DNA content of the 55 E. arundinaceus accessions using flow cytometry and to identify the correlation between ploidy and phenotypic traits. Among the 55 accessions, four tetraploids and 51 hexaploids were identified. The four tetraploids originated from Mengma Yunnan, Shuangjiang Yunnan, Gaozhou Guangdong and Chengle Sichuan. The mean DNA content was 4.82 pg/2C for the tetraploid and 7.30 pg/2C for the hexaploid plants. The ploidy was negatively correlated with cellulose content and positively correlated (P<0.05) with plant height, stem diameter, leaf width, dry weight per plant, fresh weight per plant and hemicellulose content. However, ploidy was not correlated with leaf length, tiller number and the ratio of dry weight and fresh weight. This study will be useful for revealing the distribution of the ploidy of wild E. arundinaceus in Chin, traits markers analysis, and utilization of this species, such as cultivar improvement and sugarcane breeding in the future.