Search for: All records

The human visual system uses two parallel pathways for spatial processing and object recognition. In contrast, computer vision systems tend to use a single feedforward pathway, rendering them less robust, adaptive, or efficient than human vision. To bridge this gap, we developed a dual-stream vision model inspired by the human eyes and brain. At the input level, the model samples two complementary visual patterns to mimic how the human eyes use magnocellular and parvocellular retinal ganglion cells to separate retinal inputs to the brain. At the backend, the model processes the separate input patterns through two branches of convolutional neural networks (CNN) to mimic how the human brain uses the dorsal and ventral cortical pathways for parallel visual processing. The first branch (WhereCNN) samples a global view to learn spatial attention and control eye movements. The second branch (WhatCNN) samples a local view to represent the object around the fixation. Over time, the two branches interact recurrently to build a scene representation from moving fixations. We compared this model with the human brains processing the same movie and evaluated their functional alignment by linear transformation. The WhereCNN and WhatCNN branches were found to differentially match the dorsal and ventral pathways of the visual cortex, respectively, primarily due to their different learning objectives, rather than their distinctions in retinal sampling or sensitivity to attention-driven eye movements. These model-based results lead us to speculate that the distinct responses and representations of the ventral and dorsal streams are more influenced by their distinct goals in visual attention and object recognition than by their specific bias or selectivity in retinal inputs. This dual-stream model takes a further step in brain-inspired computer vision, enabling parallel neural networks to actively explore and understand the visual surroundings. 

Abstract Tree canopies are known to elevate atmospheric inputs of both mercury (Hg) and methylmercury (MeHg). While foliar uptake of gaseous Hg is well documented, little is known regarding the temporal dynamics and origins of MeHg in tree foliage, which represents typically less than 1% of total Hg in foliage. In this work, we examined the foliar total Hg and MeHg content by following the growth of five individual trees of American Beech (Fagus grandifolia) for one growing season (April–November, 2017) in North Carolina, USA. We show that similar to other studies foliar Hg content increased almost linearly over time, with daily accumulation rates ranging from 0.123 to 0.161 ng/g/day. However, not all trees showed linear increases of foliar MeHg content along the growing season; we found that 2 out of 5 trees showed elevated foliar MeHg content at the initial phase of the growing season but their MeHg content declined through early summer. However, foliar MeHg content among all 5 trees showed eventual increases through the end of the growing season, proving that foliage is a net accumulator of MeHg while foliar gain of biomass did not “dilute” MeHg content. 

Abstract Three members of the Arabidopsis AINTEGUMENTA-LIKE/PLETHORA (AIL/PLT) transcription factor family, AIL5/PLT5, AIL6/PLT3, and AIL7/PLT7, exhibit partially overlapping roles with AINTEGUMENTA (ANT) during flower development. Loss ofANTfunction alone results in smaller floral organs and female sterility indicating that some ANT functions cannot be provided by these related transcription factors. Previously, we showed that expression ofAIL6at the same levels and spatial pattern asANTcould largely rescue the defects ofantmutants. This suggested that the functional differences betweenANTandAIL6were primarily a consequence of expression differences. Here, we investigated the functional differences betweenANTand bothAIL5andAIL7by expressing these twoAILs under the control of theANTpromoter. We found that onlyANT:gAIL5lines with much higher amounts ofAIL5mRNA as compared withANTcould compensate for loss ofANTfunction.ANT:gAIL7lines withAIL7mRNA levels similar to those ofANTwere able to rescue some but not all aspects of theantmutant phenotype. Thus, expression differences alone cannot explain the functional differences between ANT and these two related proteins. Studies in yeast show that AIL5 and AIL7 have lower transcriptional activation activities as compared with ANT and AIL6 when bound to the consensus ANT DNA binding site. Our results suggest that differences in both expression and protein activity contribute to the functional specificity of ANT compared with AIL5 and AIL7. 

MicroRNA171 (miR171), a group of 21-nucleotide single-strand small RNAs, is one ancient and conserved microRNA family in land plants. This review focuses on the recent progress in understanding the role of miR171 in plant stem cell homeostasis and developmental patterning, and the regulation of miR171 by developmental cues and environmental signals. Specifically, miR171 regulates shoot meristem activity and phase transition through repressing the HAIRYMERISTEM (HAM) family genes. In the model species Arabidopsis, miR171 serves as a short-range mobile signal, which initiates in the epidermal layer of shoot meristems and moves downwards within a limited distance, to pattern the apical-basal polarity of gene expression and drive stem cell dynamics. miR171 levels are regulated by light and various abiotic stresses, suggesting miR171 may serve as a linkage between environmental factors and cell fate decisions. Furthermore, miR171 family members also demonstrate both conserved and lineage-specific functions in land plants, which are summarized and discussed here. 

Abstract In the present paper, we are with integrable discretization of a modified Camassa–Holm (mCH) equation with linear dispersion term. The key of the construction is the semidiscrete analog for a set of bilinear equations of the mCH equation. First, we show that these bilinear equations and their determinant solutions either in Gram‐type or Casorati‐type can be reduced from the discrete Kadomtsev–Petviashvili (KP) equation through Miwa transformation. Then, by scrutinizing the reduction process, we obtain a set of semidiscrete bilinear equations and their general soliton solution in Gram‐type or Casorati‐type determinant form. Finally, by defining dependent variables and discrete hodograph transformations, we are able to derive an integrable semidiscrete analog of the mCH equation. It is also shown that the semidiscrete mCH equation converges to the continuous one in the continuum limit. 

Summary The molecular mechanisms of quantitative resistance (QR) to fungal pathogens and their relationships with growth pathways are poorly understood.We identified tomato TRK1 (TPK1b Related Kinase1) and determined its functions in tomato QR and plant growth. TRK1 is a receptor‐like cytoplasmic kinase that complexes with tomato LysM Receptor Kinase (SlLYK1).SlLYK1andTRK1are required for chitin‐induced fungal resistance, accumulation of reactive oxygen species, and expression of immune response genes. Notably, TRK1 and SlLYK1 regulate SlMYC2, a major transcriptional regulator of jasmonic acid (JA) responses and fungal resistance, at transcriptional and post‐transcriptional levels.Further, TRK1 is also required for maintenance of proper meristem growth, as revealed by the ectopic meristematic activity, enhanced branching, and altered floral structures inTRK1RNAi plants. Consistently, TRK1 interacts with SlCLV1 and SlWUS, andTRK1RNAi plants show increased expression ofSlCLV3andSlWUSin shoot apices. Interestingly, TRK1 suppresses chitin‐induced gene expression in meristems but promotes expression of the same genes in leaves. SlCLV1 and TRK1 perform contrasting functions in defense but similar functions in plant growth.Overall, through molecular and biochemical interactions with critical regulators, TRK1 links upstream defense and growth signals to downstream factor in fungal resistance and growth homeostasis response regulators. 

SUMMARY The shoot apical meristems (SAMs) of land plants are crucial for plant growth and organ formation. In several angiosperms, theHAIRY MERISTEM(HAM) genes function as key regulators that control meristem development and stem cell homeostasis. To date, the origin and evolutionary history of the HAM family in land plants remains unclear. Potentially shared and divergent functions of HAM family members from angiosperms and non‐angiosperms are also not known. In constructing a comprehensive phylogeny of the HAM family, we show that HAM proteins are widely present in land plants and that HAM proteins originated prior to the divergence of bryophytes. The HAM family was duplicated in a common ancestor of angiosperms, leading to two distinct groups: type I and type II. Type‐II HAM members are widely present in angiosperms, whereas type‐I HAM members were independently lost in different orders of monocots. Furthermore, HAM members from angiosperms and non‐angiosperms (including bryophytes, lycophytes, ferns and gymnosperms) are able to replace the role of the type‐IIHAMgenes in Arabidopsis, maintaining established SAMs and promoting the initiation of new stem cell niches. Our results uncover the conserved functions of HAM family members and reveal the conserved regulatory mechanisms underlying HAM expression patterning in meristems, providing insight into the evolution of key stem cell regulators in land plants.