Modulation of starch synthesis in Arabidopsis via phytochrome B-mediated light signal transduction

Starch is a major storage carbohydrate in plants and is critical in crop yield and quality.Starch synthesis is intricately regulated by internal metabolic processes and external environmental cues;however,the precise molecular mechanisms governing this process remain largely unknown.In this study,we revealed that high red to far-red(high R:FR)light significantly induces the synthesis of leaf starch and the expression of synthesis-related genes,whereas low R:FR light suppress these processes.Arabidopsis phytochrome B(phyB),the primary R and FR photoreceptor,was identified as a critical positive regulator in this process.Downstream of phyB,basic leucine zipper transcription factor ELONGATED HYPOCOTYL5(HY5)was found to enhance starch synthesis,whereas the basic helix-loop-helix transcription factors PHYTOCHROME INTERACTING FACTORs(PIF3,PIF4,and PIF5)inhibit starch synthesis in Arabidopsis leaves.Notably,HY5 and PIFs directly compete for binding to a shared G-box cis-element in the promoter region of genes encoding starch synthases GBSS,SS3,and SS4,which leads to antagonistic regulation of their expression and,consequently,starch synthesis.Our findings highlight the vital role of phyB in enhancing starch synthesis by stabilizing HY5 and facilitating PIFs degradation under high R:FR light conditions.Conversely,under low R:FR light,PIFs predominantly inhibit starch synthesis.This study provides insight into the physiological and molecular functions of phyB and its downstream transcription factors HY5 and PIFs in starch synthesis regulation,shedding light on the regulatory mechanism by which plants synchronize dynamic light signals with metabolic cues to module starch synthesis.

Design and Gait Planning of a Worm-inspired Metameric Robot for Pipe Crawling

The earthworm has been attracted much attention in the research and development of biomimetic robots due to their unique locomotion mechanism,compact structure,and small motion space.This paper presents a new design and prototype of a worm-inspired metameric robot with a movement pattern similar to that of earthworms.The robot consists of multiple telescopic modules connected in series through joint modules.The telescopic module mimics the contraction and elongation motion modes of the earthworm segments.A kinematic and dynamic analysis is conducted on the telescopic module,and an input torque calculation method is provided to ensure sufficient friction between the robot and the pipe wall.The gait modes of the prototype robot for straight and turning locomotion are introduced,and these modes are extended to robots constructed by different numbers of telescopic modules.In addition,a method is proposed to increase the friction between the robot and the pipe wall in the aforementioned gait modes without changing the robot structure,thereby improving the robot’s motion ability in pipelines.The theoretical model of gait modes has also been validated through gait experiments.The findings of this paper would provide a useful basis for the design,modeling,and control of future worm inspired robots.

Histological and single-nucleus transcriptome analyses reveal the specialized functions of ligular sclerenchyma cells and key regulators of leaf angle in maize

Leaf angle(LA)is a crucial factor that affects planting density and yield in maize.However,the regulatory mechanisms underlying LA formation remain largely unknown.In this study,we performed a comparative histological analysis of the ligular region across various maize inbred lines and revealed that LA is significantly influenced by a two-step regulatory process involving initial cell elongation followed by subsequent lignification in the ligular adaxial sclerenchyma cells(SCs).Subsequently,we performed both bulk and single-nucleus RNA sequencing,generated a comprehensive transcriptomic atlas of the ligular region,and identified numerous genes enriched in the hypodermal cells that may influence their specialization into SCs.Furthermore,we functionally characterized two genes encoding atypical basic-helix-loop-helix(bHLH)transcription factors,bHLH30 and its homolog bHLH155,which are highly expressed in the elongated adaxial cells.Genetic analyses revealed that bHLH30 and bHLH155 positively regulate LA expansion,and molecular experiments demonstrated their ability to activate the transcription of genes involved in cell elongation and lignification of SCs.These findings highlight the specialized functions of ligular adaxial SCs in LA regulation by restricting further extension of ligular cells and enhancing mechanical strength.The transcriptomic atlas of the ligular region at single-nucleus resolution not only deepens our understanding of LA regulation but also enables identification of numerous potential targets for optimizing plant architecture in modern maize breeding.

Regulation of Leaf Angle by Auricle Development n Maize

In plants, the leaf angle （LA） affects how densely crops can be planted and thus is one of factors determining grain yield per acre. This complex quantitative trait is controlled by developmental signals, hormones, and environmental factors （Luo et al., 2016）.