[Differential protein analysis on the root response of rice with high phosphorous uptake efficiency to low phosphorous stress].

A comparative proteomics analysis was performed to identify the molecular response of a rice cultivar (Oryza sative cv. 'IRRI71331') with high phosphorous (P) uptake efficiency to low P stress. The hydroponically grown rice plants were provided with two levels of P (0.5 mg x L(-1) and 10 mg x L(-1)) supplied in quarter strength Kimura solution, and the root total proteins extracted on the 3rd and 6th day of treatments were separated by two-dimensional gel electrophoresis (2-DE). Comparing with the control (10 mg x L(-1) of P), a total of 29 protein spots under low P stress (0.5 mg x L(-1)) showed differences in their relative abundance, among which, 17 were higher, 11 were lower, and 1 was novel on the 3rd day, and 8 were induced, 19 were suppressed, 1 was disappeared, and 1 had no obvious change on the 6th day. Ten differentially expressed protein spots were identified by MALDI-TOF/MS, and searched in protein databases. According to the putative functions, the identified proteins were classified into four groups, i.e., signal transduction (glycine-rich RNA-binding protein, phosphate starvation response regulator-like), gene expression (putative pre-mRNA splicing factor, putative AAA-metalloprotease), metabolism (adenylosuccinate lyase, serpin, S-adenosylmethionine synthetase, MYB transcription factor-like protein), and ion transport (cation-transporting ATPase, sarcoplasmic reticulum protein). The identified proteins were involved in various physiological responses to enhance stress resistance, such as signal recognition and transduction, RNA cleavage, degradation of denatured protein, and ion transportation and cellular ion balance. The serine protease inhibitor and S-adenosylmethionine synthetase and the MYB transcription factor-like protein, which were the key proteins associated with P deficiency--tolerance of other species, were affected by the same stress for rice. The results indicated that the tolerance to low P stress was controlled by a complex signal transduction and metabolism regulation network in rice root system.

[Assesment of genetic diversity of allelopathic rice germplasm based on RAPD and ISSR].

Random Amplified Polymorphic DNA (RAPD) and Inter-simple Sequence Repeat (ISSR) methods were used to detect the genetic diversity of 57 allelopathic rice accessions which were introduced from 10 countries or areas. A total of 12 RAPD primers and seven ISSR primers were indentified with polymorphism among the entries. For RAPD markers, 85 polymorphic bands were produced, percentage of polymorphic bands (PPB) were 69.4%. For ISSR marker, 34 polymorphic bands were generated, PPB were 53.0%. The result from the clustering analysis by UPGMA indicated that those accessions from the same geographical location were clustered into one group. It was also found that some rice accessions with higher allelopathic potential were clustered together, implying that the genes conferring allelopathy in those rice accessions might be isolocus. However, some rice accessions with different allelopathic potential clustered into the same group performed lower level of generic polymorphism which was attributed to oriented selection for other traits in breeding program. The estimates of correlation coefficient of RAPD and ISSR based on the genetic similarity matrices were significantly correlated.