Bulked segregant analysis reveals candidate genes responsible for dwarf formation in woody oilseed crop castor bean

Plant dwarfism is a desirable agronomic trait in non-timber trees, but little is known about the physiological and molecular mechanism underlying dwarfism in woody plants. Castor bean (Ricinus communis) is a typical woody oilseed crop. We performed cytological observations within xylem, phloem and cambia tissues, revealing that divergent cell growth in all tissues might play a role in the dwarf phenotype in cultivated castor bean. Based on bulked segregant analyses for a F2 population generated from the crossing of a tall and a dwarf accession, we identified two QTLs associated with plant height, covering 325 candidate genes. One of these, Rc5NG4-1 encoding a putative IAA transport protein localized in the tonoplast was functionally characterized. A non-synonymous SNP (altering the amino acid sequence from Y to C at position 218) differentiated the tall and dwarf plants and we confirmed, through heterologous yeast transformation, that the IAA uptake capacities of Rc5NG4-1Y and Rc5NG4-1C were significantly different. This study provides insights into the physiological and molecular mechanisms of dwarfing in woody non-timber economically important plants, with potential to aid in the genetic breeding of castor bean and other related crops.

626 Improving the yeast transformation efficiency for yeast display in antibody development

BackgroundIn the therapeutic antibody development process, the yeast display technology which expresses a large library of antibodies is very useful for increasing the affinity of a lead antibody. Ideally, a yeast library should exceed the size of 10E10 to 10E11 to get close to the real affinity maturation process. However, due to low transformation efficiency with yeast, it requires trememdous scaling-up efforts to simply reach the 10E9 library size.MethodsTo address the transformation problem, we developed a new electroporation device that applies a high voltage on a sealed electroporation tube containing the yeast and plasmids in a low conductance buffer.ResultsThe new device is arcing free due to the sealed design and each single reaction could generate 10E8 library size, far exceeding the 10E6 size that was previously reported in a single reaction.ConclusionsWith the improved transformation efficiency, it becomes very straightforward to reach the currently difficult size of 10E9. Further more, it is possible to reach the 10E10 to 10E11 library size with reaction scaling-up. Our new method could be very useful for the field of antibody development.

Free fatty acids promote transformation efficiency of yeast

ABSTRACT High transformation efficiency is essential in genetic engineering for functional metabolic analysis and cell factory construction, in particular in construction of long biosynthetic pathways with multiple genes. Here, we found that free fatty acid (FFA)-overproducing strain showed higher transformation efficiency in Saccharomyces cerevisiae. We then verified that external supplementation of FFAs, to the culture media for competent cell preparation, improved yeast transformation efficiency significantly. Among all tested FFAs, 0.5 g/L C16:0 FFA worked best on promoting transformation of S. cerevisiae and Komagataella phaffii (previously named as Pichia pastoris). Furthermore, C16:0 FFA improved the assembly efficiency of multiple DNA fragments into large plasmids and genome by 100%, which will facilitate the construction and optimization of multigene-containing long pathways.

Yeast transformation efficiency is enhanced by TORC1- and eisosome-dependent signalling

ABSTRACTTransformation of baker’s yeast (Saccharomyces cerevisiae) plays a key role in several experimental techniques, yet the molecular mechanisms underpinning transformation are still unclear. Addition of amino acids to the growth and transformation medium increases transformation efficiency. Here, we show that target of rapamycin complex 1 (TORC1) activated by amino acids enhances transformation via ubiquitin-mediated endocytosis. We created mutants of the TORC1 pathway, α-arrestins, and eisosome-related genes. Our results demonstrate that the TORC1-Npr1-Art1/Rsp5 pathway regulates yeast transformation. Based on our previous study, activation of this pathway results in a 13-fold increase in transformation efficiency, or greater. Additionally, we suggest DNA is taken up by domains at the membrane compartment of Can1 (MCC) in the plasma membrane formed by eisosomes. Yeast studies on transformation could be used as a platform to understand the mechanism of DNA uptake in mammalian systems, which is clinically relevant to optimise gene therapy.