Reduced grain chalkiness and its possible physiological mechanism in transgenic rice overexpressing L-GalLDH

Chalkiness is one of the key factors determining rice quality and price. Ascorbic acid(Asc) is a major plant antioxidant that performs many functions in plants. L-Galactono-1,4-lactone dehydrogenase(L-Gal LDH, EC1.3.2.3) is an enzyme that catalyzes the final step of Asc biosynthesis in plants. Here we show that the L-Gal LDH-overexpressing transgenic rice, GO-2,which has constitutively higher leaf Asc content than wild-type(WT) plants, exhibits significantly reduced grain chalkiness. Higher foliar ascorbate/dehydroascorbate(Asc/DHA)ratios at 40, 60, 80, and 100 days of plant age were observed in GO-2. Further investigation showed that the enhanced level of Asc resulted in a significantly higher ribulose-1,5-bisphosphate(Ru BP) carboxylase/oxygenase(Rubisco) protein level in GO-2 at 80 days. In addition, levels of abscisic acid(ABA) and jasmonic acid(JA) were lower in GO-2 at 60, 80, and100 days. The results we present here indicate that the enhanced level of Asc is likely responsible for changing redox homeostasis in key developmental stages associated with grain filling and alters grain chalkiness in the L-Gal LDH-overexpressing transgenic by maintaining photosynthetic function and affecting phytohormones associated with grain filling.

Nutritional Composition and Assessment of Gracilaria lemaneiformis Bory

The chemical composition, mineral elements, vitamins, free fatty acids and amino acid content of the edible red alga Gracilaria lemaneiformis Bory, grown in the sea near Nan＇ao island, Guangdong Province, were analyzed in the present study. Gracilaria lemaneiformis Bory showed a total sugar content of 14.65%. The protein content was 21%, of which approximately 41% was determined to be essential amino acids （EAA）. The major amino acid components were glutamic acid, leucine, arginine, and alanine. Of the EAA assayed, methionine and cysteine appeared to be the most limiting amino acids compared with the EAA pattern provided by Food and Agricultural Organization of the United Nations. The total lipids content was 0.87% and comprised a high composition of unsaturated fatty acids （61%）, mainly as linoleic acid and oleic acid, and a little amount of polyunsaturated fatty acid; palmitic acid was the main component （39%） of saturated acids. Relatively high levels of vitamin C, iodine, phosphorus, and zinc were also present in G. lemaneiformis. The nutritional composition between G. lemaneiformis and Nostoc flagelliforme, a rare alga that is widely eaten in Chinese society, was compared. The results suggest that N. flagelliforme can be substituted for by G. lemaneiformis, not only because of their similar shape, but also because of their approximate nutritional composition. Gracilaria lemaneiformis may possibly serve as a potential healthy food in human diets in the future.

A Putative Chloroplast-Localized Ca2＋/H＋ Antiporter CCHA1 Is Involved in Calcium and pH Homeostasis and Required for PSII Function in Arabidopsis

Calcium is important for chloroplast, not only in its photosynthetic but also nonphotosynthetic functions. Mul- tiple Ca2＋/H＋ transporters and channels have been described and studied in the plasma membrane and organ- elle membranes of plant cells; however, the molecular identity and physiological roles of chloroplast Ca2＋/H＋ antiporters have remained unknown. Here we report the identification and characterization of a member of the UPFO016 family, CCHA1 （a chloroplast-localized potential Ca2＋/H＋ antiporter）, in Arabidopsis thaliana. We observed that the ccha I mutant plants developed pale green leaves and showed severely stunted growth along with impaired photosystem II （PSII） function. CCHA1 localizes to the chloroplasts, and the levels of the PSII core subunits and the oxygen-evolving complex were significantly decreased in the ccha I mutants compared with the wild type. In high Ca2＋ concentrations, Arabidopsis CCHA1 partially rescued the growth defect of yeast gdtl3 null mutant, which is defective in a Ca2＋/H＋ antiporter. The cchal mutant plants also showed significant sensitivity to high concentrations of CaCI2 and MnCI2, as well as variation in pH. Taken these results together, we propose that CCHA 1 might encode a putative chloroplast-localized Ca2＋/H＋ antiporter with critical functions in the regulation of PSII and in chloroplast Ca2＋ and pH homeostasis in Arabidopsis.

Expression of multi-domain type III antifreeze proteins from the Antarctic eelpout (Lycodichths dearborni) in transgenic tobacco plants improves cold resistance

Type III antifreeze proteins(AFPIIIs)are a group of small globular proteins found in some polar fishes to protect them against freezing damage.Transgenic expression of AFPs has been shown to confer cold tolerance to commercially important plants and animals.We have previously isolated multiple AFPIII genes in the Antarctic eelpout(Lycodichthys dearborni)that encode larger AFPIII isoforms with up to 12 of the conventional domains.Here we have introduced the fish AFPIII genes that encode for the monomer(ld1),dimer(ld2),trimer(ld3)and tetramer(ld4)AFPIII isoforms in tobacco plants.Pot-grown 4-week-old transgenic tobacco plants were exposed to cold stress at 4◦C for 30 days and the results show that ld1,ld2,ld3 and ld4 transgenic plants present relatively lower electrolyte leakage and lower content of malondialdehyde(MDA),but accumulated higher content of proline when compared to control plants.This indicates considerable improved membrane integrity under low temperature stress and improvement of the plant cold resistance.The plants transformed with the AFPIII tetramer-and trimer-domains demonstrated a higher cold-tolerant levels when compared with plants transformed with the dimer-and monomer AFPIII domains.Our study further supports that fish AFPIIIs,especially the multidomain proteins,protect cells from non-freezing hypothermic stresses,apart from there well-known function as ice inhibitors molecules at freezing temperature.

The invasive potential of a hybrid species: insights from soil chemical properties and soil microbial communities

作为适应性进化,入侵物种与本土物种的自然杂交威胁着全球生物多样性。然而,杂交种的潜在入侵机制尚未得到系统研究,尤其是在土壤化学性质和土壤微生物群落方面。在一个为期两年的田间试验中,对入侵种南美蟛蜞菊(Sphagneticola trilobata)和杂交蟛蜞菊(南美蟛蜞菊与本地蟛蜞菊S.calendulacea杂交)的土壤微生物群落、土壤解钾菌和解磷菌菌落数、土壤酶活性以及叶片光饱和速率进行了测定。结果表明:杂交蟛蜞菊土壤可溶性有机碳和解磷菌菌落数显著高于南美蟛蜞菊和本地蟛蜞菊。土壤酸性磷酸酶、总PLFA、细菌PLFA、真菌PLFA、纤维素酶、脲酶在三种处理间无显著差异。杂交蟛蜞菊光饱和光合速率、光合氮、磷和钾利用效率显著高于入侵种南美蟛蜞菊,但与本地蟛蜞菊无显著差异。杂交蟛蜞菊总生物量和根生物量显著高于本地蟛蜞菊。因此,与本地蟛蜞菊相比,杂交蟛蜞菊仍然有较高的入侵性,其未来可能加剧本地蟛蜞菊的灭绝。

Anthocyanin accumulation in juvenile Schima superba leaves is a growth trade-off by consuming energy for adaptation to high light during summer

Aims Anthocyanin accumulation is the main factor underlying why young plant leaves turn red,and plant growth follows the principle of maximizing the economic efficiency of energy.There is a need to verify the role of young plant leaves turning red and confirm whether anthocyanin accumulation overconsumes the energy of the plant.Methods We compared the different pigment contents,antioxidant capaci-ties,leaf mass per area,photosynthetic characteristics,dark res-piration rates,light compensation points(LCPs)and electron flow distribution of young and mature Schima superba leaves grown under full sunlight and 30%full sunlight conditions.We then exam-ined the correlations between anthocyanins and total antioxidant capacity,photosynthetic pigments,dark respiration rates,LCPs by using linear regression.Finally,we analyzed Pearson correlation coefficients and used principal component analysis to evaluate the interactions of these functional indicators.Important Findings The young leaves of S.superba accumulated anthocyanins in full sunlight but not in 30%full sunlight.Anthocyanins substantially con-tributed to the total antioxidant capacity(accounting for 33.29%)in juvenile S.superba leaves.Young leaves containing more anthocyanin accumulated less reactive oxygen species after high light(HL)treat-ment.However,juvenile leaves accumulating anthocyanins showed 56.97%higher dark respiration rates,24.79%higher LCPs and 5.32%higher allocations of electron flow to photorespiration and lower organic substance accumulation than did those without anthocyanins.These results suggest that young S.superba leaves must consume more energy to accumulate anthocyanins to adapt to HL environments.Therefore,plants sacrifice growth rate to ensure survival,which is a trade-off for their ability to respond to external environments.