生命科学最新文献

Cytokinins regulate diverse aspects of plant development. They are perceived by membrane-localised receptors that transmit a signal to nuclear-localised response regulators via the Histidine Phosphotransfer proteins (HPts). These HPts can be divided into two classes: authentic HPts (AHPs), which positively regulate cytokinin signalling, and pseudo HPts (PHPs), which inhibit it. Whilst four of the five Arabidopsis AHPs form a well-conserved monophyletic clade, AHP4 evolved separately and is more closely related to the monocot PHPs than to the dicot AHPs. AHP4's role in cytokinin signalling has been ambiguous; in some cases, it has been shown to act as a positive regulator, whilst in others, it acts negatively. Here, we propose that AHP4 act like a dimmer switch to dampen cytokinin output. Under optimal growth conditions, AHP4 is expressed at a low level in the phloem companion cells and has little effect on either cytokinin signalling or plant development. However, AHP4 expression is induced under osmotic stress, and under this condition, we show a novel role for AHP4 in reducing cytokinin signalling in the phloem and maintaining primary root growth. We propose that AHP4 fine-tunes responses to the osmotic environment by attenuating cytokinin signalling.

Drought poses a significant threat to global rice production, and a comparative study between rice and wheat serves as an essential approach to unravel the mechanisms relating to drought tolerance. This study examined the differential responses of gas exchange, leaf hydraulic conductance, and leaf morpho-anatomical traits in Shanyou 63 (Oryza sativa) and Yannong 19 (Triticum aestivum). Our findings revealed that rice photosynthesis was more sensitive to drought than wheat, primarily due to greater reductions in stomatal conductance (g_s) and mesophyll conductance (g_m). The larger reduction of g_s in rice was related to a more substantial decrease in leaf hydraulic conductance, which was driven by more severe downsizing of leaf xylem conduits and the thickened mestome cell walls. The more severe depression of g_m in rice under drought was associated with the decreased chloroplast surface area exposed to intercellular airspaces and cell wall porosity (φ/τ) as well as the thickened mesophyll cell walls (T_cw-mes). The thicker T_cw-mes and the decreased φ/τ may be related to the biosynthesis and deposition of cellulose and hemicellulose. This study provides evidence that the regulation of cell wall components and the retention of leaf morphological and anatomical structures play a critical role in maintaining a high photosynthetic capacity under drought stress.

High molecular weight glutenin subunits (HMW-GSs) are critical grain storage proteins in wheat, which govern its unique processing quality. A HMW-GS 1Dy10 allele variant (1Dy10-m619SN), carrying a serine-to-asparagine substitution at the 619th residue, undergoes partial posttranslational cleavage. This modification leads to improved cookie-making quality. However, the enzymes mediating this cleavage remain unknown. In this study, we identified vacuolar processing enzymes (VPEs) as candidates for 1Dy10-m619SN processing using TurboID-based proximity labeling and RNA-seq analysis. In vitro cleavage assays confirmed that VPEs catalyzed 1Dy10-m619SN cleavage. Phylogenic analysis revealed that there are two seed-type VPEs in wheat, TaVPEI and TaVPEII, with TaVPEI being further subdivided into TaVPEI-1, TaVPEI-2, and TaVPEI-3. Despite sharing conserved catalytic domains, these isoforms display distinct temporal expression patterns, with TaVPEI-1 expression showing the strongest correlation with the posttranslational cleavage of 1Dy10-m619SN. TaVPEI-1 protein is localized to the vacuole, the well-known deposition site for HMW-GSs. Overexpression of TaVPEI-1 in wheat enhances the 1Dy10-m619SN cleavage. Collectively, these findings demonstrate that the seed-type VPEs in wheat are responsible for the posttranslational cleavage of 1Dy10-m619SN, which provides new insights into the molecular basis of wheat's unique processing quality.

Key message

Divergent shrub growth-temperature relationships were observed in adjacent shrubline sites under similar climates, demonstrating that site-specific factors such as topographic conditions modulate shrub growth sensitivity to climate warming.

Abstract

Alpine shrubs are expected to show enhanced growth and upslope shifts as climate keeps warming. However, climate-growth relationships are often contingent on site conditions. Herein, the climate–growth relationships of alpine R. aganniphum shrubs were investigated at a dry (LZ45) and a wet (GB45) site located at an elevation of above 4500 m on the southeastern Tibetan Plateau. Ring-width data were collected from 50 Rhododendron shrubs, and two standardized ring-width chronologies spanning 143 and 178 years were developed for LZ45 and GB45 sites, respectively. Minimum winter temperature was identified as the most significant climatic constraint of shrub radial growth at the dry site, whereas warmer summer conditions enhanced growth at the wet site. Results of linear mixed-effects models demonstrated that combining climatic and topographic factors improved the explained variance of shrub growth at both sites. A lower value of soil moisture and topographic wetness index in the dry site resulted in a lower growth confirming the importance of water shortage in that site. By synthesizing findings on alpine Rhododendron shrubs across several regions, this study highlights the topographical modulation of growth responses of alpine shrubs to climate change. Alpine Rhododendron shrubs in dry sites may be at an increasing risk of growth decline under warmer and drier future climate conditions, with negative implications for alpine ecosystems. Our study illustrates how regional climate and site conditions should be carefully accounted when studying alpine woody communities.

Bread wheat (Triticum aestivum L.) is an allohexaploid (AABBDD) whose three ancestral subgenomes generate complex patterns of gene regulation. Most genes exist as homoeologous triads, and the relative expression balance among copies, homoeolog expression bias, is central to polyploid evolution and adaptation. Recent high-quality assemblies, long-read transcriptomics, and pan-transcriptome resources have uncovered extensive cultivar-specific transcriptional diversity. Because transposable elements (TEs) compose over 80% of the wheat genome, they are prime candidates for shaping subgenome asymmetry. We synthesize recent pan-genomic and transcriptomic evidence, including genome-wide associations between TE insertions and genome-specific expression, and propose a unifying framework in which TEs modulate homoeolog expression by donating cis-regulatory sequences, altering chromatin states, producing small RNAs, and driving structural variation. We discuss experimental and computational challenges for establishing causality, and outline future functional and translational strategies to leverage TE-associated regulatory diversity in wheat breeding.