7,680 research outputs found
Evolution of the RALF Gene Family in Plants: Gene Duplication and Selection Patterns
Rapid alkalinization factors (RALFs) are plant small peptides that could induce a rapid pH increase in the medium of plant cell suspension culture and play a critical role in plant development. The evolutionary process of the RALF gene family remains unclear. To obtain details of the phylogeny of these genes, this study characterized RALF genes in Arabidopsis, rice, poplar and maize. Phylogenetic trees, evolutionary patterns and molecular evolutionary rates were used to elucidate the evolutionary process of this gene family. In addition, the different signatures of selection, expression patterns, and subcellular localization of RALFs were also analyzed. We found that the RALF gene family had a rapid birth process after the separation of the eudicot and monocot species about 145 million years ago, that tandem duplication played a dominant role in the expansion of Arabidopsis and rice RALF gene family, and that RALFs were under purifying selection according to estimations of the substitution rates of these genes. We also identified a diverse expression pattern of RALF genes and predominant extracellular localization feature of RALF proteins. Our findings shed light on several key differences in RALF gene family evolution among the plant species, which may provide a scaffold for future functional analysis of this family
Coupling the valley degree of freedom to antiferromagnetic order
Conventional electronics are based invariably on the intrinsic degrees of
freedom of an electron, namely, its charge and spin. The exploration of novel
electronic degrees of freedom has important implications in both basic quantum
physics and advanced information technology. Valley as a new electronic degree
of freedom has received considerable attention in recent years. In this paper,
we develop the theory of spin and valley physics of an antiferromagnetic
honeycomb lattice. We show that by coupling the valley degree of freedom to
antiferromagnetic order, there is an emergent electronic degree of freedom
characterized by the product of spin and valley indices, which leads to
spin-valley dependent optical selection rule and Berry curvature-induced
topological quantum transport. These properties will enable optical
polarization in the spin-valley space, and electrical detection/manipulation
through the induced spin, valley and charge fluxes. The domain walls of an
antiferromagnetic honeycomb lattice harbors valley-protected edge states that
support spin-dependent transport. Finally, we employ first principles
calculations to show that the proposed optoelectronic properties can be
realized in antiferromagnetic manganese chalcogenophosphates (MnPX_3, X = S,
Se) in monolayer form.Comment: 6 pages, 5 figure
SkillNet-X: A Multilingual Multitask Model with Sparsely Activated Skills
Traditional multitask learning methods basically can only exploit common
knowledge in task- or language-wise, which lose either cross-language or
cross-task knowledge. This paper proposes a general multilingual multitask
model, named SkillNet-X, which enables a single model to tackle many different
tasks from different languages. To this end, we define several
language-specific skills and task-specific skills, each of which corresponds to
a skill module. SkillNet-X sparsely activates parts of the skill modules which
are relevant either to the target task or the target language. Acting as
knowledge transit hubs, skill modules are capable of absorbing task-related
knowledge and language-related knowledge consecutively. Based on Transformer,
we modify the multi-head attention layer and the feed forward network layer to
accommodate skill modules. We evaluate SkillNet-X on eleven natural language
understanding datasets in four languages. Results show that SkillNet-X performs
better than task-specific baselines and two multitask learning baselines (i.e.,
dense joint model and Mixture-of-Experts model). Furthermore, skill
pre-training further improves the performance of SkillNet-X on almost all
datasets. To investigate the generalization of our model, we conduct
experiments on two new tasks and find that SkillNet-X significantly outperforms
baselines
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