Biology subjects

Hildebrand, D.

Publications and source records attributed to Hildebrand, D..

3 recordsLinked to original sources

bioRxiv2021

Different DGAT1s show different TAG synthesis abilities and a specific amino acid substitution enhances oil accumulation

Triacylglycerols (TAGs) are the major component of plant storage lipids. Acyl-CoA:diacylglycerol acyltransferase (DGAT) catalyzes the final step of the Kennedy pathway, and responsible for plant oil accumulation. We previously found DGAT activity of Vernonia galamensis DGAT1 was distinctively higher than that of Arabidopsis thaliana DGAT1 and soybean DGAT1 in a yeast microsome assay. In this study, the DGAT1 cDNAs of Arabidopsis, Vernonia, soybean, and castor were introduced into Arabidopsis (ecotype Col-0). All Vernonia DGAT1 expressing lines showed a significantly higher oil content (average 49% relative increase compared to the wild type) followed by soybean, and castor. Most Arabidopsis DGAT1 over-expressing lines did not show a significant increase. In addition to these four DGAT1s, sunflower, Jatropha and sesame DGAT1 genes were introduced into the TAG biosynthesis defective yeast mutant (H1246). In the yeast expression culture, DGAT1s from Arabidopsis, castor, and soybean only slightly increased TAG content, however, DGAT1s from Vernonia, sunflower, Jatropha, and sesame remarkably increased TAG content more than 10 times higher than the former three DGAT1s. Three amino acid residues were characteristically common in the latter four DGAT1s. Using soybean DGAT1, these amino acid substitutions by site-directed mutagenesis was performed and analyzed. These substitutions substantially increased the TAG content. HighlightDGAT1s from several plant species were tested their TAG accumulation promotion in Arabidopsis and yeast. They were divided into high and low function and single amino acid substitution enhanced function

plant biology↗

bioRxiv2020

Response of Prosopis farcta to copper and cadmium stress and potential for accumulation and translocation of these heavy metals

Few studies have evaluated the effects of various levels of heavy metals on medicinal plants. The impact of gradually increased soil levels of copper (Cu) and cadmium (Cd) on the medicinal plant native to Southwest Asia and North Africa, Prosopis farcta, irrigated with metal-enriched water was determined. The exposure of plants to Cd or Cu decreased plant growth and increased Cd and Cu concentration in their shoots and roots. External Cd or Cu in the soil increased the uptake of both elements. Regression analysis showed that the weight of both shoots and roots decreased linearly with the increase of Cu and Cd contents in roots and shoots. Results showed that Cd was more toxic than Cu. The water content of shoots and roots decreased linearly with increased heavy metal levels. P. farcta could take up Cu and Cd in both Cu- and Cd-contaminated soils, however, it was more capable for transporting Cd from roots to shoots rather than Cu. P. farcta is a natural accumulator for Cu and Cd under gradually increased levels of these metals in the soil.

plant biology↗

bioRxiv2020

Central vestibular tuning arises from patterned convergence of otolith afferents

As sensory information moves through the brain, higher-order areas exhibit more complex tuning than lower areas. Though models predict this complexity is due to convergent inputs from neurons with diverse response properties, in most vertebrate systems convergence has only been inferred rather than tested directly. Here we measure sensory computations in zebrafish vestibular neurons across multiple axes in vivo. We establish that whole-cell physiological recordings reveal tuning of individual vestibular afferent inputs and their postsynaptic targets. An independent approach, serial section electron microscopy, supports the inferred connectivity. We find that afferents with similar or differing preferred directions converge on central vestibular neurons, conferring more simple or complex tuning, respectively. Our data also resolve a long-standing contradiction between anatomical and physiological analyses by revealing that sensory responses are produced by sparse but powerful inputs from vestibular afferents. Together these results provide a direct, quantifiable demonstration of feedforward input convergence in vivo.

neuroscience↗