Heterologous Expression of ATG8c from Soybean Confers Tolerance to Nitrogen Deficiency and Increases Yield in Arabidopsis

Nitrogen is an essential element for plant growth and yield. Improving Nitrogen Use Efficiency (NUE) of crops could potentially reduce the application of chemical fertilizer and alleviate environmental damage. To identify new NUE genes is therefore an important task in molecular breeding. Macroautophagy (autophagy) is an intracellular process in which damaged or obsolete cytoplasmic components are encapsulated in double membraned vesicles termed autophagosomes, then delivered to the vacuole for degradation and nutrient recycling. One of the core components of autophagosome formation, ATG8, has been shown to directly mediate autophagosome expansion, and the transcript of which is highly inducible upon starvation. Therefore, we postulated that certain homologs of Saccharomyces cerevisiae ATG8 (ScATG8) from crop species could have potential for NUE crop breeding. A soybean (Glycine max, cv. Zhonghuang-13) ATG8, GmATG8c, was selected from the 11 family members based on transcript analysis upon nitrogen deprivation. GmATG8c could partially complement the yeast atg8 mutant. Constitutive expression of GmATG8c in soybean callus cells not only enhanced nitrogen starvation tolerance of the cells but accelerated the growth of the calli. Transgenic Arabidopsis over-expressing GmATG8c performed better under extended nitrogen and carbon starvation conditions. Meanwhile, under optimum growth conditions, the transgenic plants grew faster, bolted earlier, produced larger primary and axillary inflorescences, eventually produced more seeds than the wild-type. In average, the yield was improved by 12.9%. We conclude that GmATG8c may serve as an excellent candidate for breeding crops with enhanced NUE and better yield

Gap size effects on tree regeneration in afforestations of Black pine (Pinus nigra Arn.)

The authors deal with the problem of the re-naturalization of afforestations of Black pine in the Apennines (Central Italy). Gap-cutting of two different sizes (the gap diameter/stand height ratios were respectively 0.75 and 1.0) on age classes stands (respectively 50 and 90 years old) have been carried out. The results of the dynamics of the tree regeneration established in the gaps 7 years after the beginning of the experiment are given. The Black pine represents the best regenerated tree species and its presence is increasing. Some broadleaves, Pubescent oak (Quercus pubescens Willd.) and Holm oak (Quercus ilex L.) particularly, and Hop-hornbeam (Ostrya carpinifolia Scop.) and Manna-ash (Fraxinus ornus L.) on a subordinate way, are also present in the gaps. These results confirm that the gap-cutting system represents an effective instrument for the natural regeneration priming and a low impact environmental treatment which is particularly fit for the re-naturalization of the conifers’ monocultures. According to this experience the gaps’ optimal sizes are 150-250 m2. These gaps should be distributed appropriately in space and time