ATP-binding motifs play key roles in Krp1p, kinesin-related protein 1, function for bi-polar growth control in fission yeast

Construction of an Efficient Agrobacterium tumefaciens-Based Transformation System in the Entomopathogenic fungus Metahizium rileyi

Metarhizium rileyi is a filamentous entomopathogenic fungus that is highly pathogenic to lepidopteran insects. In our study, we constructed an Agrobacterium tumefaciens-mediated transgene system using the hygromycin resistance gene (Hyg R) as a selection marker in M. rileyi through homologous recombination. Binary knockout vectors for two genes (NOR_03501, longevity assurance gene, and NOR_03153, ATP-binding domain protein domain gene) in the M. rileyi strain SZCY201010 were successfully developed. We compared the genetic transformation efficiency using five kinds of asexual spores. The initial genetic transformation rates using a competent blastospore for NOR_03501 and NOR_03153 were 54.35 and 47.19%, respectively. Subsequently, both genes were successfully knocked out, and the transformed fungi were verified by PCR, RT-qPCR, and green fluorescent protein labeling. The biological phenotypes of the two genes were analyzed. The NOR_03501 gene plays a crucial role in carbon source utilization, stress resistance, and cuticle infection of fungal mycelium growth, while the NOR_03153 gene is significant for conidial production, stress resistance, and body wall infection. This study provides a promising tool for gene manipulation in M. rileyi, enhancing research in functional genomics and the exploration of fungal gene resources.

A malectin domain kinesin functions in pollen and seed development in Arabidopsis

The kinesin family is greatly expanded in plants compared with animals and, with more than a third up-regulated in expression during cell division, it has been suggested that this expansion facilitated complex plant-specific cytoskeletal rearrangements. The cell cycle-regulated kinesins include two with an N-terminal malectin domain, a protein domain that has been shown to bind polysaccharides and peptides when found extracellularly in receptor-like kinases. Although malectin domain kinesins are evolutionarily deep rooted, their function in plants remains unclear. Here we show that loss of MALECTIN DOMAIN KINESIN 2 (MDKIN2) results in stochastic developmental defects in pollen, embryo, and endosperm. High rates of seed abnormalities and abortion occur in mdkin2 mutants through a partial maternal effect. No additive effect or additional developmental defects were noted in mdkin1 mdkin2 double mutants. MDKIN2 is expressed in regions of cell division throughout the plant. Subcellular localization of MDKIN2 indicates a role in cell division, with a possible secondary function in the nuclei. Our results reveal a non-essential but important role for a malectin domain kinesin during development in plants.

A unique kinesin-like protein, Klp8, is involved in mitosis and cell morphology through microtubule stabilization

Kinesins are microtubule (MT)-based motors involved in various cellular functions including intracellular transport of vesicles and organelles, and dynamics of chromosomes during cell division. The fission yeast Schizosaccharomyces pombe expresses nine kinesin-like proteins (klps). Klp8 is one of them and has not been characterized yet though it has been reported to localize at the division site. Here, we studied function and localization of Klp8 in S. pombe cells. The gene klp8⁺ was not essential for both viability and cytoskeletal organization. Klp8-YFP was concentrated as medial cortical dots during interphase, and organized into a ring at the division site during mitosis. The Klp8 ring seemed to be localized in the space between the actomyosin contractile ring and the plasma membrane. The Klp8 ring shrank as cytokinesis proceeded. In klp8-deleted (Δ) cells, the speed of spindle elongation during anaphase B was slowed down. Overproduction of Klp8 caused bent or elongated cells, in which MTs were abnormally elongated and less dynamic than those in normal cells. Deletion of klp8⁺ gene suppressed the delay in mitotic entry in blt1Δ cells. These results suggest that Klp8 is involved in mitosis and cell morphology through MT stabilization.

The yeast actin cytoskeleton

The actin cytoskeleton is a complex network of dynamic polymers, which plays an important role in various fundamental cellular processes, including maintenance of cell shape, polarity, cell division, cell migration, endocytosis, vesicular trafficking, and mechanosensation. Precise spatiotemporal assembly and disassembly of actin structures is regulated by the coordinated activity of about 100 highly conserved accessory proteins, which nucleate, elongate, cross-link, and sever actin filaments. Both in vivo studies in a wide range of organisms from yeast to metazoans and in vitro studies of purified proteins have helped shape the current understanding of actin dynamics and function. Molecular genetics, genome-wide functional analysis, sophisticated real-time imaging, and ultrastructural studies in concert with biochemical analysis have made yeast an attractive model to understand the actin cytoskeleton, its molecular dynamics, and physiological function. Studies of the yeast actin cytoskeleton have contributed substantially in defining the universal mechanism regulating actin assembly and disassembly in eukaryotes. Here, we review some of the important insights generated by the study of actin cytoskeleton in two important yeast models the budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe.