Biofertilizing Effect of Chlorella sorokiniana Suspensions on Wheat Growth

Journal of Plant Growth Regulation - The potential of microalgae as a biofertilizer in agriculture is increasingly recognized. We studied the effect of applications of Chlorella on growth of wheat...     

Bacillus methylotrophicus M4-96 Stimulates the Growth of Strawberry (Fragaria × ananassa ‘Aromas’) Plants In Vitro and Slows Botrytis cinerea Infection by Two Different Methods of Interaction

Bacillus methylotrophicus M4-96 is a beneficial rhizobacterium that has been isolated from the rhizosphere of maize (Zea mays). In this study, we investigated its efficacy as a plant growth promoter for strawberry in vitro, as well as its ability to induce callose deposition in leaves to reduce the severity of Botrytis cinerea infection. Two methods of plant-bacterial interaction were used: inoculation near the root and emission of volatile compounds with no physical contact. Plant biomass increased under both treatments, but with developmental parameters of the plants differentially stimulated by each method. Root inoculation increased petiole number and root length, whereas bacterial volatiles increased petiole length and root number. A chemical analysis of the bacterial culture revealed the presence of indole acetic acid (0.21 μg L⁻¹) and gibberellic acid (6.16 μg L⁻¹). Acetoin was previously identified as the major volatile produced by the bacteria, and its application to strawberry explants increased their growth and development. Furthermore, when acetoin and both phytoregulators were added to the culture media, these positive effects were enhanced. The inoculation method also affected the size and quantity of callose deposits in the leaves. Treatment with volatiles increased callose deposition in the leaves by up to five-fold, which promoted a rapid defense reaction that inhibited the incidence of gray mold by reinforcing cell wall. Taken together, our results show that B. methylotrophicus M4-96 promotes growth and induces systemic resistance in strawberry plants.

     

Exogenous nitric oxide causes collapse of retinal ganglion cell axonal growth cones in vitro

We show that nitric oxide (NO) from applied NO-donating chemicals induces collapse of ganglion cell axonal growth cones extending from explants of tadpole retina in culture. Peroxynitrite, a neurotoxic product of NO and superoxide reaction, did not induce collapse, and oxyhemoglobin, which binds NO, blocked the highly effective collapsing activity of the NO donor S-nitrosocysteine. Membrane-permeable analogs of cyclic guanosine monophosphate had no collapsing activity. Inhibitors of NO synthase did not induce collapse. NO is a potential retrograde messenger through which postsynaptic neurons signal to their inputs to modify synaptic efficacy following NMDA receptor activation. Our results suggest a role for NO as such a messenger during development of the retinotectal projection. © 1996 John Wiley & Sons, Inc.     

Using continuous directed evolution to improve enzymes for plant applications

Continuous directed evolution of enzymes and other proteins in microbial hosts is capable of outperforming classical directed evolution by executing hypermutation and selection concurrently in vivo, at scale, with minimal manual input. Provided that a target enzyme’s activity can be coupled to growth of the host cells, the activity can be improved simply by selecting for growth. Like all directed evolution, the continuous version requires no prior mechanistic knowledge of the target. Continuous directed evolution is thus a powerful way to modify plant or non-plant enzymes for use in plant metabolic research and engineering. Here, we first describe the basic features of the yeast (Saccharomyces cerevisiae) OrthoRep system for continuous directed evolution and compare it briefly with other systems. We then give a step-by-step account of three ways in which OrthoRep can be deployed to evolve primary metabolic enzymes, using a THI4 thiazole synthase as an example and illustrating the mutational outcomes obtained. We close by outlining applications of OrthoRep that serve growing demands (i) to change the characteristics of plant enzymes destined for return to plants, and (ii) to adapt (“plantize”) enzymes from prokaryotes—especially exotic prokaryotes—to function well in mild, plant-like conditions.

Continuous directed evolution using the yeast OrthoRep system is a powerful way to improve enzymes for use in plant engineering as illustrated by “plantizing” a bacterial thiamin synthesis enzyme.     

Isolation and characterization of pLS 1 plasmid mutants with increased copy numbers

Abstract Streptococcus pneumoniae genetic systems designed for isolation of plasmid mutants with copy-up phenotypes have been developed. The target plasmids have the pLS1 replicon, and two different strategies have been followed: (i) selection of clones exhibiting augmented resistance to antibiotics, or (ii) obligatory co-existence of incompatible plasmids. We have isolated 23 plasmid mutants exhibiting increased number of copies. All the mutations corresponded to four different alleles of the copG gene of plasmid pLS1. These strategies could be used with other plasmids.