Association between physical activity and allostatic load among pregnant women.

Allostatic load (AL) in pregnant women is associated with maternal and infant health outcomes. Whether physical activity (PA) is a modifiable factor associated with AL during pregnancy is unknown. In this cross-sectional study, including 725 pregnant women in 3 different trimesters, 8 biomarkers were included, and the high-risk quartile approach based on sample distribution was used to construct AL index (ALI). ALI <2 was defined as a low level and ≥2 as a high level. Student's t-test or Mann-Whitney U test and chi-squared test or Fisher exact test were used to compare differences in AL with different demographic characteristics among pregnant women. The relationship between PA and AL in pregnant women was analyzed using a binary logistic regression model. The results show that the detection rate of high-risk AL during pregnancy was 47.3%. In the adjusted model, sufficient PA was related to a lower AL than insufficient PA (OR = .693, 95%CI:.494,.971; p = .033). Compared with low- and high-intensity PAs, moderate-intensity PA was associated with lower AL (OR = .645, 95%CI:.447,.930; p = .019). The results suggest that PA is a modifiable factor related to AL, and intervention is recommended to be carried out in the first trimester to prevent the increased likelihood of high AL as pregnancy progresses. In addition, health care personnel should encourage pregnant women to participate in PA, especially moderate-intensity PA, in order to obtain lower AL and promote maternal and child health.

Transient stimulated Raman scattering spectroscopy and imaging.

Stimulated Raman scattering (SRS) has been developed as an essential quantitative contrast for chemical imaging in recent years. However, while spectral lines near the natural linewidth limit can be routinely achieved by state-of-the-art spontaneous Raman microscopes, spectral broadening is inevitable for current mainstream SRS imaging methods. This is because those SRS signals are all measured in the frequency domain. There is a compromise between sensitivity and spectral resolution: as the nonlinear process benefits from pulsed excitations, the fundamental time-energy uncertainty limits the spectral resolution. Besides, the spectral range and acquisition speed are mutually restricted. Here we report transient stimulated Raman scattering (T-SRS), an alternative time-domain strategy that bypasses all these fundamental conjugations. T-SRS is achieved by quantum coherence manipulation: we encode the vibrational oscillations in the stimulated Raman loss (SRL) signal by femtosecond pulse-pair sequence excited vibrational wave packet interference. The Raman spectrum was then achieved by Fourier transform of the time-domain SRL signal. Since all Raman modes are impulsively and simultaneously excited, T-SRS features the natural-linewidth-limit spectral line shapes, laser-bandwidth-determined spectral range, and improved sensitivity. With ~150-fs laser pulses, we boost the sensitivity of typical Raman modes to the sub-mM level. With all-plane-mirror high-speed time-delay scanning, we further demonstrated hyperspectral SRS imaging of live-cell metabolism and high-density multiplexed imaging with the natural-linewidth-limit spectral resolution. T-SRS shall find valuable applications for advanced Raman imaging.

Transient Stimulated Raman Excited Fluorescence Spectroscopy.

The pursuit of better sensitivity has always been one of the central themes in Raman spectroscopy. Recently, all-far-field single-molecule Raman spectroscopy has been demonstrated by a novel hybrid spectroscopy that couples Raman scattering with fluorescence emission. However, such frequency-domain spectroscopy lacks efficient hyperspectral excitation methods and encounters intrinsic strong fluorescence backgrounds from electronic transitions, hindering its applications in advanced Raman spectroscopy and microscopy. Here we report the ultrafast time-domain spectroscopy counterpart named transient stimulated Raman excited fluorescence (T-SREF): excited by two successive broadband femtosecond pulse pairs (i.e., the pump and Stokes pulses) with time-delay scanning, strong vibrational wave packet interference is revealed on the time-domain fluorescence trace, resulting in background-free spectra of the corresponding Raman modes after the Fourier transform. T-SREF achieves background-free Raman spectra of electronic-coupled vibrational modes with sensitivity up to the level of a few molecules, which paves the way for supermultiplexed fluorescence detection and molecular dynamics sensing.

Time-course observation of the reconstruction of stem cell niche in the intact root.

The stem cell niche (SCN) is critical in maintaining continuous postembryonic growth of the plant root. During their growth in soil, plant roots are often challenged by various biotic or abiotic stresses, resulting in damage to the SCN. This can be repaired by the reconstruction of a functional SCN. Previous studies examining the SCN's reconstruction often introduce physical damage including laser ablation or surgical excision. In this study, we performed a time-course observation of the SCN reconstruction in pWOX5:icals3m roots, an inducible system that causes non-invasive SCN differentiation upon induction of estradiol on Arabidopsis (Arabidopsis thaliana) root. We found a stage-dependent reconstruction of SCN in pWOX5:icals3m roots, with division-driven anatomic reorganization in the early stage of the SCN recovery, and cell fate specification of new SCN in later stages. During the recovery of the SCN, the local accumulation of auxin was coincident with the cell division pattern, exhibiting a spatial shift in the root tip. In the early stage, division mostly occurred in the neighboring stele to the SCN position, while division in endodermal layers seemed to contribute more in the later stages, when the SCN was specified. The precise re-positioning of SCN seemed to be determined by mutual antagonism between auxin and cytokinin, a conserved mechanism that also regulates damage-induced root regeneration. Our results thus provide time-course information about the reconstruction of SCN in intact Arabidopsis roots, which highlights the stage-dependent re-patterning in response to differentiated quiescent center.

Hydrogen peroxide homeostasis provides beneficial micro-environment for SHR-mediated periclinal division in Arabidopsis root.

The precise regulation of asymmetric cell division (ACD) is essential for plant organogenesis. In Arabidopsis roots, SHORT-ROOT (SHR) functions to promote periclinal division in cortex/endodermis initials, which generate the ground tissue patterning. Although multiple downstream transcription factors and interplaying hormone pathways have been reported, the cellular mechanism that affects SHR-mediated periclinal division remains largely unclear. Here, we found that SHR can substantially elevate reactive oxygen species (ROS) levels in Arabidopsis roots by activating respiratory burst oxidase homologs (RBOHs). Among the ROS products, hydrogen peroxide (H2 O2 ) rather than superoxide (O2- ) was shown to play a critical role in SHR-mediated periclinal division. Scavenging H2 O2 could markedly impair the ability of SHR to induce periclinal division. We also show that salicylic acid (SA) can promote H2 O2 production by repressing CAT expression, which greatly increased periclinal division in root endodermis. As a result, middle cortex was more frequently formed in the endodermis of snc1, a mutant with accumulated endogenous SA and H2 O2 . In addition to RBOHs, SHR also activated the SA pathway, which might contribute to the elevated H2 O2 level induced by SHR. Thus, our data suggest a mechanism by which SHR creates the optimal micro-environment for periclinal division by maintaining ROS homeostasis in Arabidopsis roots.

GOLVEN peptide signalling through RGI receptors and MPK6 restricts asymmetric cell division during lateral root initiation.

During lateral root initiation, lateral root founder cells undergo asymmetric cell divisions that generate daughter cells with different sizes and fates, a prerequisite for correct primordium organogenesis. An excess of the GLV6/RGF8 peptide disrupts these initial asymmetric cell divisions, resulting in more symmetric divisions and the failure to achieve lateral root organogenesis. Here, we show that loss-of-function GLV6 and its homologue GLV10 increase asymmetric cell divisions during lateral root initiation, and we identified three members of the RGF1 INSENSITIVE/RGF1 receptor subfamily as likely GLV receptors in this process. Through a suppressor screen, we found that MITOGEN-ACTIVATED PROTEIN KINASE6 is a downstream regulator of the GLV pathway. Our data indicate that GLV6 and GLV10 act as inhibitors of asymmetric cell divisions and signal through RGF1 INSENSITIVE receptors and MITOGEN-ACTIVATED PROTEIN KINASE6 to restrict the number of initial asymmetric cell divisions that take place during lateral root initiation.

Construction of a Functional Casparian Strip in Non-endodermal Lineages Is Orchestrated by Two Parallel Signaling Systems in Arabidopsis thaliana.

The Casparian strip in the root endodermis forms an apoplastic barrier between vascular tissues and outer ground tissues to enforce selective absorption of water and nutrients. Because of its cell-type specificity, the presence of a Casparian strip is used as a marker for a functional endodermis. Here, we examine the minimal regulators required for reprograming non-endodermal cells to build a functional Casparian strip. We demonstrate that the transcription factor SHORT-ROOT (SHR) serves as a master regulator and promotes Casparian strip formation through two independent activities: inducing the expression of essential Casparian strip enzymes via MYB36 and directing the subcellular localization of Casparian strip formation via SCARECROW (SCR). However, this hierarchical signaling cascade still needs SHR-independent small peptides, derived from the stele, to eventually build a functional Casparian strip in non-endodermal cells. Our study provides a synthetic approach to induce Casparian-strip-containing endodermis using a minimal network of regulators and reveals the deployment of both apoplastic and symplastic communication in the promotion of a specific cell fate.

Cell-Fate Specification in Arabidopsis Roots Requires Coordinative Action of Lineage Instruction and Positional Reprogramming.

Tissue organization and pattern formation within a multicellular organism rely on coordinated cell division and cell-fate determination. In animals, cell fates are mainly determined by a cell lineage-dependent mechanism, whereas in plants, positional information is thought to be the primary determinant of cell fates. However, our understanding of cell-fate regulation in plants mostly relies on the histological and anatomical studies on Arabidopsis (Arabidopsis thaliana) roots, which contain a single layer of each cell type in nonvascular tissues. Here, we investigate the dynamic cell-fate acquisition in modified Arabidopsis roots with additional cell layers that are artificially generated by the misexpression of SHORT-ROOT (SHR). We found that cell-fate determination in Arabidopsis roots is a dimorphic cascade with lineage inheritance dominant in the early stage of pattern formation. The inherited cell identity can subsequently be removed or modified by positional information. The instruction of cell-fate conversion is not a fast readout during root development. The final identity of a cell type is determined by the synergistic contribution from multiple layers of regulation, including symplastic communication across tissues. Our findings underline the collaborative inputs during cell-fate instruction.

Symplastic communication spatially directs local auxin biosynthesis to maintain root stem cell niche in Arabidopsis.

Stem cells serve as the source of new cells for plant development. A group of stem cells form a stem cell niche (SCN) at the root tip and in the center of the SCN are slowly dividing cells called the quiescent center (QC). QC is thought to function as a signaling hub that inhibits differentiation of surrounding stem cells. Although it has been generally assumed that cell-to-cell communication provides positional information for QC and SCN maintenance, the tools for testing this hypothesis have long been lacking. Here we exploit a system that effectively blocks plasmodesmata (PD)-mediated signaling to explore how cell-to-cell communication functions in the SCN. We showed that the symplastic signaling between the QC and adjacent cells directs the formation of local auxin maxima and establishment of AP2-domain transcription factors, PLETHORA gradients. Interestingly we found symplastic signaling is essential for local auxin biosynthesis, which acts together with auxin polar transport to provide the guidance for local auxin enrichment. Therefore, we demonstrate the crucial role of cell-to-cell communication in the SCN maintenance and further uncover a mechanism by which symplastic signaling initiates and reinforces the positional information during stem cell maintenance via auxin regulation.

Symplastic signaling instructs cell division, cell expansion, and cell polarity in the ground tissue of Arabidopsis thaliana roots.

Cell-to-cell communication is essential for the development and patterning of multicellular organisms. In plants, plasmodesmata (PD) provide direct routes for intercellular signaling. However, the role that PD-mediated signaling plays in plant development has not been fully investigated. To gain a comprehensive view of the role that symplastic signaling plays in Arabidopsis thaliana, we have taken advantage of a synthetic allele of CALLOSE SYNTHASE3 (icals3m) that inducibly disrupts cell-to-cell communication specifically at PD. Our results show that loss of symplastic signaling to and from the endodermis has very significant effects on the root, including an increase in the number of cell layers in the root and a misspecification of stele cells, as well as ground tissue. Surprisingly, loss of endodermal signaling also results in a loss of anisotropic elongation in all cells within the root, similar to what is seen in radially swollen mutants. Our results suggest that symplastic signals to and from the endodermis are critical in the coordinated growth and development of the root.