植物UV-B生理效应的分子机制研究进展

中波紫外线UV-B（280～320nm）是植物必需的太阳光线的组成部分,具有明显的双重效应：一方面UV-B在强度较高时,就触发产生大量活性氧对DNA、蛋白质以及生物膜等造成伤害,同时植物通过抗氧化系统对其作出防御反应以减轻伤害;另一方面,低强度的UV-B是植物生长发育的光信号因子之一,经由UVR8等光受体介导中、低、极低强度的UV-B信号,可能通过几个分子途径控制相关基因的表达,分别对植物的UV-B保护基因表达、形态建成、昼夜节律、生长发育等进行调控。目前对UVR8介导的低强度UV-B信号转导的分子机制研究相对深入。在本文中,将对UV-B生理效应分子机制的最新研究进展作一个比较全面的介绍。     

UV-B photoreceptor-mediated signalling in plants

Ultraviolet-B radiation (UV-B) is a key environmental signal that is specifically perceived by plants to promote UV acclimation and survival in sunlight. Whereas the plant photoreceptors for visible light are rather well characterised, the UV-B photoreceptor UVR8 was only recently described at the molecular level. Here, we review the current understanding of the UVR8 photoreceptor-mediated pathway in the context of UV-B perception mechanism, early signalling components and physiological responses. We further outline the commonalities in UV-B and visible light signalling as well as highlight differences between these pathways.     

Linking species performance to community structure as affected by UV-B radiation: an attenuation experiment

Aims UV-B radiation is known to affect plant physiology and growth rate in ways that can influence community species composition and structure. Nevertheless, comparatively little is known about how UV-B radiation induced changes in the performance of individual species cascades to affect overall community properties. Because foliage leaves are primarily responsible for photosynthesis and carbon gain and are the major organ that senses and responds to UV-B radiation, we hypothesized that, under reduced UV-B radiation, species with larger leaf areas per plant would manifest higher growth rates and hence tend to improve their community status compared to species with smaller leaf areas per plant in herbaceous plant communities.Methods We tested this hypothesis by examining plant traits (leaf area per plant and plant height), plant growth rate (aboveground biomass per plant and plant biomass per area) and community status (species within-community relative biomass) for 19 common species in a two-year field experiment in an alpine meadow on Tibetan Plateau.Important findings Aboveground biomass per plant, as well as per area, progressively increased in a 39% reduced (relative to ambient) UV-B treatment during the experimental period. At the second year, 11 out of 19 species significantly or marginally significantly increased their plant height, leaf area per plant and aboveground biomass per plant. No species was negatively affected by reducing UV-B. As hypothesized, the increase in aboveground biomass per plant increased with increasing leaf area per plant, as indicated by cross-species regression analysis. Moreover, the change in species within-community status increased with increasing leaf area per plant. Our study demonstrates that UV-B radiation has differential effects on plant growth rate across species and hence significantly affects species composition and plant community structure. We suggest that UV-B radiation is an ecological factor structuring plant communities particularly in alpine and polar areas.     

RNA-Seq Analysis Reveals MAPKKK Family Members Related to Drought Tolerance in Maize

The mitogen-activated protein kinase (MAPK) cascade is an evolutionarily conserved signal transduction pathway that is involved in plant development and stress responses. As the first component of this phosphorelay cascade, mitogen-activated protein kinase kinase kinases (MAPKKKs) act as adaptors linking upstream signaling steps to the core MAPK cascade to promote the appropriate cellular responses; however, the functions of MAPKKKs in maize are unclear. Here, we identified 71 MAPKKK genes, of which 14 were novel, based on a computational analysis of the maize (Zea mays L.) genome. Using an RNA-seq analysis in the leaf, stem and root of maize under well-watered and drought-stress conditions, we identified 5,866 differentially expressed genes (DEGs), including 8 MAPKKK genes responsive to drought stress. Many of the DEGs were enriched in processes such as drought stress, abiotic stimulus, oxidation-reduction, and metabolic processes. The other way round, DEGs involved in processes such as oxidation, photosynthesis, and starch, proline, ethylene, and salicylic acid metabolism were clearly co-expressed with the MAPKKK genes. Furthermore, a quantitative real-time PCR (qRT-PCR) analysis was performed to assess the relative expression levels of MAPKKKs. Correlation analysis revealed that there was a significant correlation between expression levels of two MAPKKKs and relative biomass responsive to drought in 8 inbred lines. Our results indicate that MAPKKKs may have important regulatory functions in drought tolerance in maize.     

萱草叶片响应低温胁迫的转录组分析

低温胁迫是萱草（Hemerocallis fulva）生长过程中经常会遭遇的一种非生物胁迫。比较了萱草叶片在低温处理（10、5、0 ℃）下转录组与对照（15 ℃）数据的差异,共筛选出差异表达基因2 457个,其中上调基因1 253个,下调基因1 204个。差异表达基因主要富集在细胞过程、代谢过程和催化活性等49个GO过程,代谢途径、次生代谢产物的生物合成、植物激素信号转导等42条KEGG代谢途径中。其中参与植物激素信号转导通路的差异表达基因发生了不同程度的变化,GH3.10基因上调至对照组的13.624倍,IAA1基因下调0.120倍;参与可溶性糖合成通路的差异基因发生了0.076~28.114倍不同程度的变化。随后对3个低温处理组共有的29个差异表达基因进行热图和网络调控分析,基于基因在网络调控中的位置,对ABCF5、OFPs和SWEETs等基因在冷应答的作用进行了分析。本研究结果为进一步挖掘萱草低温响应的关键基因及耐寒萱草种质开发、分子育种提供了一定的理论支撑。     

东乡野生稻苗期响应低温胁迫的转录组分析

为了解东乡野生稻（Oryza rufipogon）对低温胁迫的响应机制,对苗期的RNA-seq转录表达谱进行了研究。结果表明,与对照相比,共检测到10 200个差异表达基因（DEGs）,其中5 201个上调表达,4 999个下调表达,其中有426个DEGs位于已报道的水稻耐冷QTL区间,且37个为耐冷调控相关的家族基因。GO功能分类和KEGG代谢路径分析表明,核酸结合转录因子活性、氨基酸生物合成以及光合作用代谢等均参与响应低温胁迫过程。实时荧光定量分析表明,ABA响应蛋白基因、MYB转录因子和40S核糖体蛋白SA基因等12个可能与低温胁迫响应相关的DEGs表达模式与RNA-seq的一致。可见,植物激素传导途径和转录因子相关调控基因在东乡野生稻苗期响应低温胁迫过程中起重要作用。