Combined drought and heat stress in <Emphasis Type="Italic">Camellia oleifera</Emphasis> cultivars: leaf characteristics,soluble sugar and protein contents,and Rubisco gene expression

Key message

Leaf relative water content, leaf area, leaf fresh weight, and SPAD chlorophyll meter readings along with Co - rbcL and Co - rbcS expression can be used for evaluating Camellia oleifera responses to combined drought and heat stress and subsequent recovery after rainfall events.

Abstract

Leaf characteristics, soluble protein and total soluble sugar contents as well as Rubisco-related gene expression in three cultivars of C. oleifera were measured during a combined drought and heat stress period and after subsequent rainfall events. Leaf relative water content (RWC) was significantly correlated with leaf area (LA), leaf fresh weight (FW), SPAD chlorophyll meter readings, and the levels of Co-rbcL and Co-rbcS expression. Results suggest that leaf RWC, LA, leaf FW, SPAD readings together with Co-rbcL and Co-rbcS expression can be used for evaluating responses of C. oleifera cultivars to combined drought and heat stress and subsequent recovery after rainfall events. Rubisco activase might be used for evaluating plant recovery after rainfall. This study identified cultivars differing in tolerance to the combined stress and recovery. Information derived from this study should be valuable for improving survivability and productivity of C. oleifera cultivars.

     

Brassinosteroids promote development of rice pollen grains and seeds by triggering expression of Carbon Starved Anther,a MYB domain protein

Transport of photoassimilates from leaf tissues (source regions) to the sink organs is essential for plant development. Here, we show that a phytohormone, the brassinosteroids (BRs) promotes pollen and seed development in rice by directly promoting expression of Carbon Starved Anther (CSA) which encodes a MYB domain protein. Over‐expression of the BR‐synthesis gene D11 or a BR‐signaling factor OsBZR1 results in higher sugar accumulation in developing anthers and seeds, as well as higher grain yield compared with control non‐transgenic plants. Conversely, knockdown of D11 or OsBZR1 expression causes defective pollen maturation and reduced seed size and weight, with less accumulation of starch in comparison with the control. Mechanically, OsBZR1 directly promotes CSA expression and CSA directly triggers expression of sugar partitioning and metabolic genes during pollen and seed development. These findings provide insight into how BRs enhance plant reproduction and grain yield in an important agricultural crop.     

Reticulate evolution and sea‐level fluctuations together drove species diversification of slipper orchids (Paphiopedilum) in South‐East Asia

South‐East Asia covers four of the world's biodiversity hotspots, showing high species diversity and endemism. Owing to the successive expansion and contraction of distribution and the fragmentation by geographical barriers, the tropical flora greatly diversified in this region during the Tertiary, but the evolutionary tempo and mode of species diversity remain poorly investigated. Paphiopedilum, the largest genus of slipper orchids comprising nearly 100 species, is mainly distributed in South‐East Asia, providing an ideal system for exploring how plant species diversity was shaped in this region. Here, we investigated the evolutionary history of this genus with eight cpDNA regions and four low‐copy nuclear genes. Discordance between gene trees and network analysis indicates that reticulate evolution occurred in the genus. Ancestral area reconstruction suggests that vicariance and long‐distance dispersal together led to its current distribution. Diversification rate variation was detected and strongly correlated with the species diversity in subg. Paphiopedilum (~80 species). The shift of speciation rate in subg. Paphiopedilum was coincident with sea‐level fluctuations in the late Cenozoic, which could have provided ecological opportunities for speciation and created bridges or barriers for gene flow. Moreover, some other factors (e.g. sympatric distribution, incomplete reproductive barriers and clonal propagation) might also be advantageous for the formation and reproduction of hybrid species. In conclusion, our study suggests that the interplay of reticulate evolution and sea‐level fluctuations has promoted the diversification of the genus Paphiopedilum and sheds light into the evolution of Orchidaceae and the historical processes of plant species diversification in South‐East Asia.     

Angiomotin binding-induced activation of Merlin/NF2 in the Hippo pathway

The tumor suppressor Merlin/NF2 functions upstream of the core Hippo pathway kinases Lats1/2 and Mst1/2, as well as the nuclear E3 ubiquitin ligase CRL4^DCAF1. Numerous mutations of Merlin have been identified in Neurofibromatosis type 2 and other cancer patients. Despite more than two decades of research, the upstream regulator of Merlin in the Hippo pathway remains unknown. Here we show by high-resolution crystal structures that the Lats1/2-binding site on the Merlin FERM domain is physically blocked by Merlin''s auto-inhibitory tail. Angiomotin binding releases the auto-inhibition and promotes Merlin''s binding to Lats1/2. Phosphorylation of Ser518 outside the Merlin''s auto-inhibitory tail does not obviously alter Merlin''s conformation, but instead prevents angiomotin from binding and thus inhibits Hippo pathway kinase activation. Cancer-causing mutations clustered in the angiomotin-binding domain impair angiomotin-mediated Merlin activation. Our findings reveal that angiomotin and Merlin respectively interface cortical actin filaments and core kinases in Hippo signaling, and allow construction of a complete Hippo signaling pathway.     

奇古菌亚硝酸盐还原酶基因相似基因的多样性

摘要:【目的】氨氧化古菌(Ammonia-oxidizing archaea,AOA)是奇古菌门中的唯一类群,广泛分布于各个生态系统中,对氮素生物地球化学循环起着重要作用。亚硝酸还原酶是反硝化作用的关键酶,目前关于AOA反硝化作用的研究较少,对AOA 亚硝酸盐还原酶基因多样性的研究有利于揭示AOA在反硝化中的作用。【方法】本研究以水体、沉积物和土壤为研究对象,构建了奇古菌样的nirK基因克隆文库,研究了这些环境中nirK相似基因的多样性。【结果】对奇古菌样的nirK基因文库及其序列分析表明:湖水及其沉积物的 nirK基因克隆文库得到10个OTUs,菜田土壤和水样则有8个OTUs;系统发育进化树表明这些nirK氨基酸序列和Candidatus Nitrosopumilus koreensis AR1,Nitrosopumilus maritimus SCM1最为相似,但相似度较低(53%－68%)。克隆文库多样性指数分析表明:所有样品都存在不同类型的nirK基因,水体样品nirK基因类型的多样性和均匀度高于土壤样品,菜田土壤的nirK基因类型多样性最高,分布最均匀。【结论】本研究表明土壤和淡水环境中奇古菌门nirK基因也具有较高的多样性,并且这些基因型与海洋样品差异非常大,这些基因编码的亚硝酸盐还原酶可能对这些环境中的反硝化作用有重要意义。