Cloning and expression of VB12-independent methionine synthase gene responsive to alkaline stress in rice.

VB12-independent methionine synthase is present in higher plants, and catalyzes the methylation of C-homocysteine to form methionine, which is very important for methylation reactions and syntheses of polyamines and ethylene. Under the alkaline condition, using cDNA-RAPD method, a new VB12-independent methionine synthase gene has been cloned and characterized for the first time in rice in this study. The results exhibited that, the cDNA gene entailed 2740 bp, had single copy in the rice genome and encoded peptide of 765 amino acids, the peptide showed 92% and 83% identity with that from Mesembryanthemum cystallinum (U84889) and Cathararanthus roseus (X83499), respectively. It enhanced the transcription more greatly after sodium carbonate treatment for 12 h and 24 h than that of sodium chloride treatment, and then obviously reduced in 48 h later, suggesting that it is related to this stress tolerance in rice.

[Effect of temperature on the fertility restoration of different two-line hybrid rice].

On the basis of the fertility observation of hybrids from Pei'ai 64S and Nongken 58S crossed with an indica variety Nanjing11 and japonica marker line FL235, respectively, The plant growth chambers were employed to expose the F2 plant individuals to such different day mean temperature as 24 degrees C, 27 degrees C and 30 degrees C during natural long hour daylight from July to August in Wuhan (30 degrees 27' N), with a view to analyzing the difference in the temperature sensitivity of fertility between the two kinds of different fertility-restoring genes for two years running. The results showed that, whether it was under long daylight and high temperature or under long daylight and middle temperature, the mean natural seed-set percent of F1 was higher than 68.75%, suggesting that Nanjing11 could completely restore the fertility of Pei'ai 64S. And however, under natural high temperature condition, N58S x FL235 F1 could set seed naturally with 21.93%-26.75%, the mean natural seed set percent of F1 was 46.36%-48.38% in natural middle temperature condition, ability of FL235 to restore the fertility of N58S was affected by high temperature. Further analysis proved that temperature could not alter the inheritance mode of F2 but affect the extent of fertility genes expression in Nanjing11. On the other hand, the expression of fertility-genes of FL235 was sensitive to high temperature, whose the putative critical temperature was 27 degrees C, and high temperature influenced not only the genetic interactions but also the segregation modes in F2 generations.

Genetic analysis of the low critical sterility temperature point in photoperiod-thermo sensitive genic male sterile rice.

It has been a long haul but photoperiod- and thermo-sensitive genic male sterile (PTGMS) rice has not been freely used in hybrid rice production because there are two perplexing problems corresponding to the critical sterility temperature point (CSTP): the uncertainty of the CSTP segregating pattern and the instability of CSTP for every originally useful line. N5088S, the most widely commercialized japonica-type PTGMS line in China, also saw that its CSTP variants have been isolated but with all other agronomic characteristics unchanged. In this report we analyzed the genetic basis of CSTP, by employing the iterated expectation and conditional maximization (IECM) algorithm on four tiller-splitting-formed sets of seven generations from N5088S and its CSTP-variant H5088S, each set treated with one temperature regime. The main results indicated that there are two dominant major genes and polygene, as well as their respective epistasis conditioning the CSTP in the 23.5 degrees C regime. Based on the results obtained, the strategy for breeding of PTGMS lines with stable low CSTP was outlined.

[Posterior short-segment pedicle screw fixation combined with vertebroplasty for the treatment of thoracolumbar burst fractures].

OBJECTIVE: To evaluate the clinical efficacy of posterior short-segment pedicle screw fixation combined reduction of central end-plate by end-plate expand clamp and vertebroplasty with calcium phosphate cement for the treatment of thoracolumbar burst fractures. METHODS: Thirty patients with thoracolumbar burst fractures were treated with posterior pedicle screw fixation combined reduction of central end-plate by end-plate expand clamp and vertebroplasty with calcium phosphate cement. There were 22 males and 8 females with an average of 47 years (range from 25 to 71 years). Segment of fracture had 1 case in T11, 5 in T12, 14 in L1, 8 in L2, 2 in L3, 1 in L4, 1 in L5. According to Denis typing, 4 cases were type A, 25 type B, 1 type C, 1 type D, 1 type E. The relative anterior height of vertebral body and the vertebral angle were measured before and after operation and during the follow-up period (8 months after operation) through X-ray, the failure of internal fixation and recurrent kyphosis were evaluated during the follow-up period. Vertebral intracorporeal gap was measured by CT images after operation and the central end-plate fracture and reduction were observed by the reconstructed CT images (sagittal and coronary) before and after operation. RESULTS: All patients were followed up from 8 to 15 months with an average of 12 months. Relative anterior height of vertebral body and vertebral angle were well restored after operation, and there was no significant change between after operation and 8 months after operation. Preoperative,postoperative and 8 months after operation, relative anterior height of vertebral body respectively was 40.1%, 98.2%, 97.8%, vertebral angle respectively was 18.30, 2.70, 3.20. No failure of internal fixation and recurrent kyphosis were found during the follow-up period. The vertebral intracorporeal gap was about 3.1% and reduction of central endplate fracture was satisfactory. CONCLUSION: Posterior short-segment pedicle screw fixation combined with vertebroplasty with calcium phosphate cement can provide excellent reduction of post-traumatic segmental kyphosis and restore vertebral body height in the fracture level, prevent the failure of internal fixation which is an ideal method for the treatment of thoracolumbar burst fractures.

[Physiological characteristics of rice seedlings roots under aluminum stress].

A hydroponic experiment was conducted with the four-leaf stage seedlings of aluminum (Al)-susceptible rice variety IR24 and Al-tolerant rice varieties Jingyou 725 and Liangyoupeijiu to study the physiological characteristics of the seedlings roots under effects of 0, 0.5 mmol x L(-1), and 7.5 mmol x L(-1) of Al. Under the stress of 7.5 mmol Al x L(-1), Al-tolerant varieties had a far lesser decrement of root vigor than Al-susceptible variety, while the Al-susceptible variety had a higher root mitochondria H2O2 content than Al-tolerant varieties. Al stress induced a lesser increment of CAT activity in the root mitochondria of all tested varieties. With the increasing Al concentration, the root mitochondria POD activity of IR24 and Jingyou 725 decreased after an initial increase while that of Liangyoupeijiu was increasing, and the root mitochondria APX activity of IR24 decreased after an initial increase while that of Jingyou 725 and Liangyoupeijiu was increasing. The root glutamic acid content of all tested varieties showed an increase-decline trend, and their citric acid content decreased while PEP content increased. The ratio of cyanide-resistant respiration rate to total respiration rate of Al-tolerant Jingyou 725 and Liangyoupeijiu increased obviously, compared with that of Al-susceptible IR24.

[Individual and interactive effects of aluminum, selenium, silicon and phosphorus on rice seedlings growth].

By using quadratic orthogonal rotation combinatorial design, and taking aluminum (Al), selenium (Se), silicon (Si), and phosphorus (P) as test factors, the regression models of test factors and the survival rate (SR), shoot mass per hundred plants (SMHP), root mass per one hundred plant seedlings (RMHP), and proline contents (PC) of rice seedlings were established, with the individual and interactive effects of the factors analyzed. The individual effects of test factors on the SR, SMHP, RMHP, and PC of rice seedlings decreased in the order of Al > P > Se > Si. Al showed negative effect, while Se, Si, and P showed positive effect. There were no significant interactive effects between the factors, except between Al and Si. Simulated optimization test showed that rice seedlings could grow better in an Al-containing solution when the Al was within the range of 0.587-0.913 mmol L(-1), Se was of 0.478-0.564 mg x L(-1), Si was of 0.613-1.069 mmol x L(-1), and P was of 2.252-2.657 mmol L(-1).