Species-specific responses to drought,salinity and their interactions in Populus euphratica and P. pruinosa seedlings

干旱和盐胁迫是严重的非生物胁迫因子,限制植物的生长和生产力,特别是在沙漠地区。本研究采用两种沙漠杨树—胡杨(Populus euphratica)和灰杨(P. pruinosa)幼苗,比较它们对干旱、盐胁迫和两者交互胁迫的耐受性。研究了在干旱、盐胁迫和交互胁迫下,胡杨和灰杨在生长、光合能力和色素含量、非结构性碳水化合物浓度、Cl⁻分配、渗透调节和活性氧积累等方面的物种特异性响应。研究结果表明, 与胡杨相比,灰杨在干旱、盐胁迫,特别是交互胁迫下表现出更高的生长抑制作用,光合作用下降,气孔关闭和活性氧积累,抗氧化酶活性和渗透调节能力下降。此外,在盐胁迫下,胡杨限制了盐从根部向叶片的转运,并且向粗根分配的Cl⁻较多,向叶片分配的Cl⁻较少,而灰杨向叶片分配较多的Cl⁻。表明这两种杨树存在着物种特异性变化,在干旱、盐胁迫,特别是交互胁迫下,灰杨受到更大的负面作用。因此,在未来干旱和盐胁迫加重的气候环境下,在生态恢复和植树造林时,应考虑这两种杨树对干旱和盐胁迫的物种特异性响应和耐受性。     

iTRAQ‐based quantitative proteomic analysis gives insight into sexually different metabolic processes of poplars under nitrogen and phosphorus deficiencies

Male and female poplars (Populus cathayana Rehd.) respond differently to nitrogen (N) and phosphorus (P) deficiencies. In this study, an iTRAQ‐based quantitative proteomic analysis was performed. N and P deficiencies caused 189 and 144 proteins to change in abundance in males and 244 and 464 in females, respectively. Compared to N‐ and P‐deficient males, both N‐ and P‐deficient females showed a wider range of changes in proteins that are involved in amino acid, carbohydrate and protein metabolism, and the sexual differences were significant. When comparing the effects of N‐ and P‐deficiencies, N‐deficient females expressed more changes in proteins that are involved in stress responses and gene expression regulation, while P‐deficient females showed more changes in proteins that are involved in energy and lipid metabolism, stress responses and gene expression regulation. The quantitative RT‐PCR analysis of stress‐related proteins showed that males have a better expression correlation between mRNA and protein levels than do females. This study shows that P. cathayana females are more sensitive and have more rapid metabolic mechanisms when responding to N and P deficiencies than do males, and P deficiency has a wider range of effects on females than does N deficiency.     

Sex‐specific responses of Populus yunnanensis exposed to elevated CO2 and salinity

Populus yunnanensis Dode., a native dioecious woody plant in southwestern China, was employed as a model species to study sex‐specific morphological, physiological and biochemical responses to elevated CO₂ and salinity. To investigate the effects of elevated CO₂, salinity and their combination, the cuttings were exposed to two CO₂ regimes (ambient CO₂ and double ambient CO₂) and two salt treatments in growth chambers. Males exhibited greater downregulation of net photosynthesis rate (A_net) and carboxylation efficiency (CE) than females at elevated CO₂, whereas these sexual differences were lessened under salt stress. On the other hand, salinity induced a higher decrease in A_net and CE, more growth inhibition and leaf Cl^? accumulation and more damage to cell organelles in females than in males, whereas the sexual differences in photosynthesis and growth were lessened at elevated CO₂. Moreover, elevated CO₂ exacerbated membrane lipid peroxidation and organelle damage in females but not in males under salt stress. Our results indicated that: (1) females are more sensitive and suffer from greater negative effects than do males under salt stress, and elevated CO₂ lessens the sexual differences in photosynthesis and growth under salt stress; (2) elevated CO₂ tends to aggravate the negative effects of salinity in females; and (3) sex‐specific reactions under the combination of elevated CO₂ and salinity are distinct from single‐stress responses. Therefore, these results provide evidence for different adaptive responses between plants of different sexes exposed to elevated CO₂ and salinity.     

水稻OsWRKY转录因子对非生物胁迫响应的重叠表达特性分析

WRKY转录因子是植物一类比较大的基因家族,在水稻中已鉴定出102个成员。研究表明WRKY转录因子在植物生长发育、抗病耐逆等方面都具有重要的作用。本研究利用基因芯片数据结合实时定量分析,对水稻Os WRKY转录因子基因在不同的非生物逆境下的表达进行了分析,发现至少有33个Os WRKY基因同时对任何两种非生物胁迫因子做出响应,且所选20个基因中,13个基因可被ABA所诱导。OsWRKY基因这种重叠表达的特性,预示着这些基因在非生物逆境中具有功能多效性,对于培育抗逆境水稻品种具有重要的理论与实践意义。     

Analysis of differentially expressed genes in abiotic stress response and their role in signal transduction pathways

The study of abiotic stress response of plants is important because they have to cope with environmental changes to survive. The plant genomes have evolved to meet environmental challenges. Salt, temperature, and drought are the main abiotic stresses. The tolerance and response to stress vary differently in plants. The idea was to analyze the genes showing differential expression under abiotic stresses. There are many pathways connecting the perception of external stimuli to cellular responses. In plants, these pathways play an important role in the transduction of abiotic stresses. In the present study, the gene expression data have been analyzed for their involvement in different steps of signaling pathways. The conserved genes were analyzed for their role in each pathway. The functional annotations of these genes and their response under abiotic stresses in other plant species were also studied. The enzymes of signal pathways, showing similarity with conserved genes, were analyzed for their role in different abiotic stresses. Our findings will help to understand the expression of genes in response to various abiotic stresses. These genes may be used to study the response of different abiotic stresses in other plant species and the molecular basis of stress tolerance.     

Genomewide discovery of DNA polymorphisms in rice cultivars with contrasting drought and salinity stress response and their functional relevance

Next‐generation sequencing technologies provide opportunities to understand the genetic basis of phenotypic differences, such as abiotic stress response, even in the closely related cultivars via identification of large number of DNA polymorphisms. We performed whole‐genome resequencing of three rice cultivars with contrasting responses to drought and salinity stress (sensitive IR64, drought‐tolerant Nagina 22 and salinity‐tolerant Pokkali). More than 356 million 90‐bp paired‐end reads were generated, which provided about 85% coverage of the rice genome. Applying stringent parameters, we identified a total of 1 784 583 nonredundant single‐nucleotide polymorphisms (SNPs) and 154 275 InDels between reference (Nipponbare) and the three resequenced cultivars. We detected 401 683 and 662 509 SNPs between IR64 and Pokkali, and IR64 and N22 cultivars, respectively. The distribution of DNA polymorphisms was found to be uneven across and within the rice chromosomes. One‐fourth of the SNPs and InDels were detected in genic regions, and about 3.5% of the total SNPs resulted in nonsynonymous changes. Large‐effect SNPs and InDels, which affect the integrity of the encoded protein, were also identified. Further, we identified DNA polymorphisms present in the differentially expressed genes within the known quantitative trait loci. Among these, a total of 548 SNPs in 232 genes, located in the conserved functional domains, were identified. The data presented in this study provide functional markers and promising target genes for salinity and drought tolerance and present a valuable resource for high‐throughput genotyping and molecular breeding for abiotic stress traits in rice.     

Male poplars have a stronger ability to balance growth and carbohydrate accumulation than do females in response to a short‐term potassium deficiency

Potassium (K) deficiency influences plant performance, such as ion uptake and carbohydrate transport. However, little is known about differences between males and females in response to K deficiency. In this study, dry matter accumulation, photosynthetic capacity, allocation patterns of K⁺, Na⁺ and carbohydrates, and ultrastructural changes in males and females of Populus cathayana exposed to K deficiency were investigated. The results indicated that males maintained a significantly higher K⁺ content and K⁺/Na⁺ ratio in leaves and stems than did females under K deficiency. Moreover, K deficiency significantly increased the sucrose content of females, whereas no significant effect on males was detected. In addition, a comparative analysis showed that males allocated more resources to roots, while females allocated more to leaves, which resulted in sexually different root/shoot (R/S) ratios. Transmission electron microscopic (TEM) observations showed that males suffered fewer injuries than did females. These results suggested that males have a better ability to cope with K deficiency. In addition, the combined effects of salinity and K deficiency on poplars were studied. The results indicated that salt stress aggravates the negative effects caused by K deficiency. Taken together, our study provided evidence for gender‐specific strategies in ion and carbohydrate allocation in poplars exposed to a short‐term K deficiency. In leaves and stems, the lower K⁺ accumulation inhibited sucrose translocation and resulted in a decreased R/S ratio, which may contribute to males having a stronger ability to balance growth and carbohydrate accumulation when compared with females.     

Sex‐related adaptive responses to interaction of drought and salinity in Populus yunnanensis

We used Populus yunnanensis Dode., a native dioecious species in southwestern China, as a model species to study morphological, physiological, biochemical and ultrastructural responses to drought, salinity and their combination. Females exhibited more growth inhibition, gas exchange rate depression and reactive oxygen species (ROS) accumulation; higher lipid peroxide levels, lower osmotic adjustment capacity and ascorbate–glutathione cycle enzyme activities; and more damage to cell organelles than did males under drought, salinity and especially under their combination. In addition, we found sex‐specific responses in total chlorophyll content (TC), carotenoid concentration and carbon isotope composition under different osmotic stresses. Our results indicated that: (1) females are more sensitive and suffer from greater negative effects than do males under drought, salinity and especially under their combination; (2) sexual differences in adaptive responses to drought, salinity and their combination are context dependent; and (3) sex‐specific reactions under a combination of stresses are distinct from single‐stress responses. Thus, these results provide evidence for adaptive differentiation between sexes in responses to osmotic stresses and in the sensitivity to environmental change.