Introgression lines of Solanum sitiens,a wild nightshade of the Atacama Desert,in the genome of cultivated tomato

The wild tomato relative Solanum sitiens is a xerophyte endemic to the Atacama Desert of Chile and a potential source of genes for tolerance to drought, salinity and low‐temperature stresses. However, until recently, strong breeding barriers prevented its hybridization and introgression with cultivated tomato, Solanum lycopersicum L. We overcame these barriers using embryo rescue, bridging lines and allopolyploid hybrids, and synthesized a library of introgression lines (ILs) that captures the genome of S. sitiens in the background of cultivated tomato. The IL library consists of 56 overlapping introgressions that together represent about 93% of the S. sitiens genome: 65% in homozygous and 28% in heterozygous (segregating) ILs. The breakpoints of each segment and the gaps in genome coverage were mapped by single nucleotide polymorphism (SNP) genotyping using the SolCAP SNP array. Marker‐assisted selection was used to backcross selected introgressions into tomato, to recover a uniform genetic background, to isolate recombinant sub‐lines with shorter introgressions and to select homozygous genotypes. Each IL contains a single S. sitiens chromosome segment, defined by markers, in the genetic background of cv. NC 84173, a fresh market inbred line. Large differences were observed between the lines for both qualitative and quantitative morphological traits, suggesting that the ILs contain highly divergent allelic variation. Several loci contributing to unilateral incompatibility or hybrid necrosis were mapped with the lines. This IL population will facilitate studies of the S. sitiens genome and expands the range of genetic variation available for tomato breeding and research.     

Efficiency for Gene Silencing Induction in Nicotiana Species by a Viral Satellite DNA Vector

Virus-induced gene silencing （VIGS） is a useful technique for rapid plant gene function analysis. We recently reported a new VIGS vector modified from Tomato yellow leaf curl China virus （TYLCCNV） DNAβ （DNAm β）. In this study we compared in detail DNAmβ-induced gene silencing in four Nicotiana species including N. benthamiana, N. glutinosa, N. tabacum and N. paniculata. We found that DNAmβ-induced gene silencing in the four species was distinct in developing dynamics, tissue specificity, efficiency, and constancy in the plant life span. It was most efficient in N. benthamiana, where development of VIGS was most rapid, without tissue specificity and nearly 100% efficient. DNAmβ-induced gene silencing in N. glutinosa was also efficient despite being slightly less than in N. benthamiana. It initially occurred in veins, later was scattered to mesophyll, finally led to complete silencing in whole leaves. In both species, VIGS constantly expressed until the plants died. However, DNAmβ-mediated VIGS in the other two Nicotiana species, N. tabacum and N. paniculata, was significantly less efficient. It was strictly limited within the veins of the silenced leaves, and constantly occurred only over 3-4 weeks. The upper leaves that emerged later stopped showing the silencing phenotype. DNAmβ-induced gene silencing in N. benthamiana and N. glutinosa was not significantly influenced by the growth stage when the plants were agro-inoculated, and was not sensitive to high growth temperature up to 32℃. Our results indicate that this system has great potential as a versatile VIGS system for routine functional analysis of genes in some Nicotiana species.     

CRISPR/Cas9基因组编辑技术在番茄中的应用现状及展望北大核心CSCD

CRISPR/Cas9技术是一种能够快速对基因组靶位点进行特定DNA修饰的编辑工具。该文对近年来国内外有关CRISPR/Cas9技术在改善番茄农艺性状及提高生物、非生物胁迫抗性方面的研究进展进行综述,并集中讨论了CRISPR/Cas9面临的一些问题,为该基因编辑技术在番茄的种质创新及基因功能研究方面的应用提供参考。     

番茄总皂苷对小鼠高尿酸血症的调节作用北大核心CSCD

为研究番茄总皂苷对尿酸的调节作用,该文以番茄水提物为试材,利用次黄嘌呤和氧嗪酸钾以及尿酸和氧嗪酸钾建立高尿酸模型小鼠,考察番茄总皂苷对正常小鼠及高尿酸血症小鼠尿酸排泄量、血尿酸、尿素氮、肌酐、黄嘌呤氧化酶以及脏器指数的影响。结果表明:番茄总皂苷不影响正常小鼠血尿酸水平,正常组及番茄低、中、高剂量组血尿酸值分别为(170.4±36.7)、(178.3±69.7)、(175.5±42.1)、(185.3±72.6)μmol·L^(-1);番茄总皂苷对次黄嘌呤和氧嗪酸钾联合诱导的高尿酸血症小鼠可以降低血尿酸水平,降低黄嘌呤氧化酶活性,正常组、模型组及番茄高剂量组血尿酸值分别为(140.4±36.7)、(378.3±69.7)、(278.3±62.6)μmol·L^(-1),正常组、模型组及番茄低、中、高剂量组黄嘌呤氧化酶值分别为(1.2±0.3)、(1.8±0.2)、(1.6±0.2)、(1.5±0.3)、(1.3±0.4)U·g^(-1) liver;对尿酸和氧嗪酸钾联合诱导的高尿酸血症小鼠,可降低血尿酸水平,降低黄嘌呤氧化酶活性,正常组、模型组及番茄高剂量组血尿酸值分别为(98.8±21.8)、(455.6±78.8)、(333.7±68.7)μmol·L^(-1),正常组、模型组及番茄高剂量组黄嘌呤氧化酶值分别为(2.1±0.3)、(2.5±0.2)、(2.3±0.2)U·g^(-1) liver。综上结果表明,番茄总皂苷不影响正常小鼠血尿酸水平,但能降低高尿酸模型小鼠的血尿酸水平,其机制可能与降低黄嘌呤氧化酶活性有关。     

Bundle sheath extensions affect leaf structural and physiological plasticity in response to irradiance

Coordination between structural and physiological traits is key to plants' responses to environmental fluctuations. In heterobaric leaves, bundle sheath extensions (BSEs) increase photosynthetic performance (light‐saturated rates of photosynthesis, A_max) and water transport capacity (leaf hydraulic conductance, K_leaf). However, it is not clear how BSEs affect these and other leaf developmental and physiological parameters in response to environmental conditions. The obscuravenosa (obv) mutation, found in many commercial tomato varieties, leads to absence of BSEs. We examined structural and physiological traits of tomato heterobaric and homobaric (obv) near‐isogenic lines grown at two different irradiance levels. K_leaf, minor vein density, and stomatal pore area index decreased with shading in heterobaric but not in homobaric leaves, which show similarly lower values in both conditions. Homobaric plants, on the other hand, showed increased A_max, leaf intercellular air spaces, and mesophyll surface area exposed to intercellular airspace (S_mes) in comparison with heterobaric plants when both were grown in the shade. BSEs further affected carbon isotope discrimination, a proxy for long‐term water‐use efficiency. BSEs confer plasticity in traits related to leaf structure and function in response to irradiance levels and might act as a hub integrating leaf structure, photosynthetic function, and water supply and demand.