Transcriptional, post-transcriptional, and post-translational regulation of polyunsaturated fatty acid synthase genes in Aurantiochytrium limacinum strain BL10: Responses to nitrogen starvation.

Under nitrogen deficient conditions, the Aurantiochytrium limacinum strain BL10 greatly increases the production of docosahexaenoic acid (DHA) and n-6 docosapentaenoic acid. Researchers have yet to elucidate the mechanism by which BL10 promotes the activity of polyunsaturated fatty acid synthase (Pfa), which plays a key role in the synthesis of polyunsaturated fatty acid (PUFA). Analysis in the current study revealed that in nitrogen-depleted environments, BL10 boosts the transcription and synthesis of proteins by facilitating the expression of pfa genes via transcriptional regulation. It was also determined that BL10 adjusts the lengths of the 5'- and 3'-untranslated regions (suggesting post-transcriptional regulation) and modifies the ratio of two Pfa1 isoforms to favor PUFA production via post-translational regulation (ubiquitination). These findings clarify the exceptional DHA production of BL10 and provide additional insights into the regulatory mechanisms of PUFA biosynthesis in Aurantiochytrium.

An efficient rice mutagenesis system based on suspension-cultured cells.

Plant mutants are important bio-resources for crop breeding and gene functional studies. Conventional methods for generating mutant libraries by mutagenesis of seeds with physical or chemical agents are of low efficiency. Here, we developed a highly-efficient ethyl methanesulfonate (EMS) mutagenesis system based on suspension-cultured cells, with rice (Oryza sativa L.) as an example. We show that treatment of suspension-cultured tiny cell clusters with 0.4% EMS for 18-22 h followed by differentiation and regeneration produced as high as 29.4% independent mutant lines with visible phenotypic variations, including a number of important agronomic traits such as grain size, panicle size, grain or panicle shape, tiller number and angle, heading date, male sterility, and disease sensitivity. No mosaic mutant was observed in the mutant lines tested. In this mutant library, we obtained a mutant with an abnormally elongated uppermost internode. Sequencing and functional analysis revealed that this is a new allelic mutant of eui (elongated uppermost internode) caused by two point mutations in the first exon of the EUI gene, representing a successful example of this mutagenesis system.

Do Resources Help or Hurt? The Critical Roles of Me, Others, and Organization in Mitigating Workplace Demands.

Today's job demands-resources (JD-R) literature emphasizes the interactions between job demands and resources. However, the dynamism of JD-R processes in which individuals manage to counteract the detrimental effects of job demands on employees by flexibly adjusting resources calls this relationship into question. Hence, in this study, we depict JD-R dynamics in the workplace by developing a cross-level moderated-mediation model that unveils the different roles played by job and personal resources when they are woven together with job demands. We examine how and when the relationships among three types of resources-organizationally assigned high-performance work systems (HPWSs), psychological capital (PsyCap), and social support climate (SSC)-help employees deal with excessive workload and unhealthy emotional demands. Using a two-wave research design, we measured and tested the causal relationships of the proposed variables. We found that (1) HPWSs had a negative effect on workload, (2) workload provoked employee emotional demands, (3) the interaction between HPWSs and PsyCap increased workload, and (4) SSC mitigated the positive effect of workload on employee emotional demands. This study contributes to the JD-R theory and literature by unlocking the potential roles of various resources. Theoretical and practical implications, limitations, and future research avenues are also presented.