Towards Remote Estimation of Radiation Use Efficiency in Maize Using UAV-Based Low-Cost Camera Imagery

Radiation Use Efficiency (RUE) defines the productivity with which absorbed photosynthetically active radiation (APAR) is converted to plant biomass. Readily used in crop growth models to predict dry matter accumulation, RUE is commonly determined by elaborate static sensor measurements in the field. Different definitions are used, based on total absorbed PAR (RUEtotal) or PAR absorbed by the photosynthetically active leaf tissue only (RUEgreen). Previous studies have shown that the fraction of PAR absorbed (fAPAR), which supports the assessment of RUE, can be reliably estimated via remote sensing (RS), but unfortunately at spatial resolutions too coarse for experimental agriculture. UAV-based RS offers the possibility to cover plant reflectance at very high spatial and temporal resolution, possibly covering several experimental plots in little time. We investigated if (a) UAV-based low-cost camera imagery allowed estimating RUEs in different experimental plots where maize was cultivated in the growing season of 2016, (b) those values were different from the ones previously reported in literature and (c) there was a difference between RUEtotal and RUEgreen. We determined fractional cover and canopy reflectance based on the RS imagery. Our study found that RUEtotal ranges between 4.05 and 4.59, and RUEgreen between 4.11 and 4.65. These values are higher than those published in other research articles, but not outside the range of plausibility. The difference between RUEtotal and RUEgreen was minimal, possibly due to prolonged canopy greenness induced by the stay-green trait of the cultivar grown. The procedure presented here makes time-consuming APAR measurements for determining RUE especially in large experiments superfluous

An additional regulator, TsaQ, is involved with TsaR in regulation of transport during the degradation of p-toluenesulfonate in Comamonas testosteroni T-2

The degradation of p-toluenesulfonate (TSA) by Comamonas testosteroni T-2 is initiated by a transport system (TsaST) and enzymes (TsaMBCD) encoded on the tsa transposon, Tn tsa, on the TSA plasmid (pTSA). Tn tsa comprises an insert of 15 kb between two IS 1071 elements. The left-hand 6 kb and the right-hand 6 kb are nearly mirror images. The regulator of the tsaMBCD1 genes (right-hand side) is the centrally located LysR-type TsaR, which is encoded upstream of tsaMBCD1 on the reverse strand. The other centrally located genes are tsaS and tsaT, encoded downstream of tsaR and on the same strand as both tsaR and tsaMBCD2. The latter four genes are not expressed. Downstream of tsaD1 (tsaD2) is tsaQ1 (tsaQ2) and another open reading frame of unknown function. The tsaQ genes have identical sequences. Sequence analysis indicated that TsaQ could be an IclR-type regulator, whose expression during degradation of TSA was proven by data from RT-PCR. Both copies of tsaQ could be knocked-out by homologous recombination. Double mutants failed to grow with TSA but grew with p-toluenecarboxylate (TCA), which is also degraded via TsaMBCD. This showed TsaQ to be essential for the degradation of TSA but not TCA. We attributed this to regulation of the transport of TSA, especially to regulation of the expression of tsaT, which was expressed solely during growth with TSA. Seven independently isolated bacteria containing the tsa operon were available. Those six which contained tsaT on Tn tsa also contained tsaQ. The promoter region of tsaT was found to be a target of the regulator TsaR. Band-shift data indicate that TsaR is required for the expression of tsaT, which suggests that tsaR and tsaQ(1,2), together with tsaMBCD1, belong to a common regulatory unit

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Characterization of TsaR, an Oxygen-Sensitive LysR-Type Regulator for the Degradation of p-Toluenesulfonate in Comamonas testosteroni T-2

TsaR is the putative LysR-type regulator of the tsa operon (tsaMBCD) which encodes the first steps in the degradation of p-toluenesulfonate (TSA) in Comamonas testosteroni T-2. Transposon mutagenesis was used to knock out tsaR. The resulting mutant lacked the ability to grow with TSA and p-toluenecarboxylate (TCA). Reintroduction of tsaR in trans on an expression vector reconstituted growth with TSA and TCA. The tsaR gene was cloned into Escherichia coli with a C-terminal His tag and overexpressed as TsaR(His). TsaR(His) was subject to reversible inactivation by oxygen, which markedly influenced the experimental approaches used. Gel filtration showed TsaR(His) to be a monomer in solution. Overexpressed TsaR(His) bound specifically to three regions within the promoter between the divergently transcribed tsaR and tsaMBCD. The dissociation constant (K(D)) for the whole promoter region was about 0.9 μM, and the interaction was a function of the concentration of the ligand TSA. A regulatory model for this LysR-type regulator is proposed on the basis of these data