TSC1 enables plastid development under dark conditions, contributing to rice adaptation to transplantation shock.

Since its domestication from wild rice thousands of years ago, rice has been cultivated largely through transplantation. During transplantation from the nursery to the paddy field, rice seedlings experience transplantation shock which affects their physiology and production. However, the mechanisms underlying transplantation shock and rice adaptation to this shock are largely unknown. Here, we isolated a transplant-sensitive chloroplast-deficient (tsc1) rice mutant that produces albino leaves after transplantation. Blocking light from reaching the juvenile leaves and leaf primordia caused chloroplast deficiencies in transplanted tsc1 seedlings. TSC1 encodes a noncanonical adenosine triphosphate-binding cassette (ABC) transporter homologous to AtNAP14 and is of cyanobacterial origin. We demonstrate that TSC1 controls plastid development in rice under dark conditions, and functions independently of light signaling. However, light rescued the tsc1 mutant phenotype in a spectrum-independent manner. TSC1 was upregulated following transplantation, and modulated the iron and copper levels, thereby regulating prolamellar body formation during the early P4 stage of leaf development. Therefore, TSC1 is indispensable for plastid development in the absence of light, and contributes to adaptation to transplantation shock. Our study provides insight into the regulation of plastid development and establishes a framework for improving recovery from transplantation shock in rice.

Phosphoenolpyruvate Carboxylase in Arabidopsis Leaves Plays a Crucial Role in Carbon and Nitrogen Metabolism.

Phosphoenolpyruvate carboxylase (PEPC) is a crucial enzyme that catalyzes an irreversible primary metabolic reaction in plants.Previous studies have used transgenic plants expressing ectopic PEPC forms with diminished feedback inhibition to examine the role of PEPC in carbon and nitrogen metabolism. To date, the in vivo role of PEPC in carbon and nitrogen metabolism has not been analyzed in plants. In this study, we examined the role of PEPC in plants, demonstrating that PPC1 and PPC2 were highly expressed genes encoding PEPC in Arabidopsis (Arabidopsis thaliana) leaves and that PPC1 and PPC2 accounted for approximately 93% of total PEPC activity in the leaves. A double mutant, ppc1/ppc2, was constructed that exhibited a severe growth-arrest phenotype. The ppc1/ppc2 mutant accumulated more starch and sucrose than wild-type plants when seedlings were grown under normal conditions. Physiological and metabolic analysis revealed that decreased PEPC activity in the ppc1/ppc2 mutant greatly reduced the synthesis of malate and citrate and severely suppressed ammonium assimilation. Furthermore, nitrate levels in the ppc1/ppc2 mutant were significantly lower than those in wild-type plants due to the suppression of ammonium assimilation. Interestingly, starch and sucrose accumulation could be prevented and nitrate levels could be maintained by supplying the ppc1/ppc2 mutant with exogenous malate and glutamate, suggesting that low nitrogen status resulted in the alteration of carbon metabolism and prompted the accumulation of starch and sucrose in the ppc1/ppc2 mutant. Our results demonstrate that PEPC in leaves plays a crucial role in modulating the balance of carbon and nitrogen metabolism in Arabidopsis.

BnWRI1 coordinates fatty acid biosynthesis and photosynthesis pathways during oil accumulation in rapeseed.

Photosynthesis in "green" seeds, such as rapeseed, soybean, and Arabidopsis, plays a substantial role in the improved efficiency of oil accumulation. However, the molecular mechanism underpinning the coordinated expression of fatty acid (FA) biosynthesis- and photosynthesis-related genes in such developing seeds remains to be elucidated. Here, we found that seed-specific overexpression of BnWRI1, a WRI1 homolog from rapeseed (Brassica napus cv. ZGY2), results in enhanced chlorophyll content in developing seeds and increased oil content and seed mass in matured seeds. BnWRI1 was co-expressed with BnBCCP and BnCAB, two marker genes of FA biosynthesis and photosynthesis during seed development, respectively. Overexpression of BnWRI1 increased expression of both marker genes. Further, the nuclear-localized BnWRI1 protein was found to act as a transcription activator. It could bind to the GT1-element and/or GCC-box, which are widespread in the upstream regions of genes involved in FA biosynthesis and photosynthesis pathways. Accordingly, BnWRI1 could interact with promoters of BCCP2 and LHB1B2 in vivo. These results suggested that BnWRI1 may coordinate FA biosynthesis and photosynthesis pathways in developing seeds via directly stimulating expression of GT1-element and/or GCC-box containing genes.

OsPIE1, the rice ortholog of Arabidopsis PHOTOPERIOD-INDEPENDENT EARLY FLOWERING1, is essential for embryo development.

BACKGROUND: The SWR1 complex is important for the deposition of histone variant H2A.Z into chromatin necessary to robustly regulate gene expression during growth and development. In Arabidopsis thaliana, the catalytic subunit of the SWR1-like complex, encoded by PIE1 (PHOTOPERIOD-INDEPENDENT EARLY FLOWERING1), has been shown to function in multiple developmental processes including flowering time pathways and petal number regulation. However, the function of the PIE1 orthologs in monocots remains unknown. METHODOLOGY/FINDINGS: We report the identification of the rice (Oryza sativa) ortholog, OsPIE1. Although OsPIE1 does not exhibit a conserved exon/intron structure as Arabidopsis PIE1, its encoded protein is highly similar to PIE1, sharing 53.9% amino acid sequence identity. OsPIE1 also has a very similar expression pattern as PIE1. Furthermore, transgenic expression of OsPIE1 completely rescued both early flowering and extra petal number phenotypes of the Arabidopsis pie1-2 mutant. However, homozygous T-DNA insertional mutants of OsPIE1 in rice were embryonically lethal, in contrast to the viable mutants in the orthologous genes for yeast, Drosophila and Arabidopsis (Swr1, DOMINO and PIE1, respectively). CONCLUSIONS/SIGNIFICANCE: Taken together, our results suggest that OsPIE1 is the rice ortholog of Arabidopsis PIE1 and plays an essential role in rice embryo development.

[Raising fat content in transgenic rice by anti-PEP gene transformation].

Gene for phosphoenolpyruvate carboxylase (PEPCase) was incorporated in antisense orientation into genome of japonica rice variety Xiushui 11 through Agrobacterium tumefaciens-mediated transformation of mature seeds-derived embryogenic calli, and a total of 95 transgenic plants were regenerated, which were confirmed by histochemical detection of GUS activity (Fig.2), PCR assay (Fig.3) and Southern hybridization analysis (Fig.4). The transgene was inherited by the T1 progeny and Mendelian 3:1 segregation ratio was observed in most transgenic lines. It was found that the fat content of hulled grains of T2 transgenic lines was 0.37 +/- 0.12 per cent higher than that of the control, most of which were statistically very significant (Table 2).

Highly efficient transformation and plant regeneration of tall fescue mediated by Agrobacterium tumefaciens.

An efficient and reproducible system has been developed for the production of transgenic plants in tall fescue (Festuca arundinacea Schreb.) using A. tumefaciens-mediated transformation. Two-months-old suspension cultures served as excellent explants for transformation. The explants were inoculated with an A. tumefaciens strain EHA105 carrying a plasmid pDBA121 containing genes for hygromycin phosphotransferase (hpt) and phosphinotricin acetyltransferase (bar). The commercial herbicide Basta was used as a selective agent. Inclusion of acetosyringone (ACS) 20 mg/L in the co-culture medium led to an increase in transformation efficiency. The efficiency of transformation was highly dependent on the genotype, the explant, the culture medium and selective agent used. Tall fescue transformation efficiency is 2.85-10.9 plants per gram fresh weight (FW) of suspension cultures. This is much higher than the corresponding values reported before (2-5 plants). So far more than 300 transgenic plants have been obtained, the fertility of some transgenic plants had decreased. Stable integration and high expression of the transgenes were confirmed by PCR analysis and Southern blot hybridization or herbicide Basta spraying test.

[Evaluation of topotecan combined with cisplatin in the treatment of small cell lung cancer].

BACKGROUND: To evaluate the effects and toxicities of topotecan combined with cisplatin in the treatment of small cell lung cancer (SCLC). METHODS: Twenty-six patients with SCLC diagnosed by pathologic or cytologic examination were treated with topotecan 1.25 mg/(m²*d) on days 1-5 and cisplatin 25 mg/(m²*d) on days 1-3. The chemotherapy was repeated every 21 days as a cycle. RESULTS: Out of 26 evaluable patients, 3 achieved complete response and 11 achieved partial response with an overall response rate of 53.8%. The response rates were 75.0% and 35.7% in 12 previously untreated patients and 14 patients with prior chemotherapy, respectively. In addition, one of eight refractory patients and two of five patients with brain metastasis got partial responses. The median survival period was 27 weeks and one-year survival rate was 38.5%. Myelosuppression was the major dose-limiting toxicity. CONCLUSIONS: Topotecan combined with cisplatin is effective for SCLC and it toxicity is tolerable.