Project description:The small RNAs and their targets were characterized in lettuce (Lactuca sativa) genome by deep sequencing the small RNA populations of leaf tissues (cv. Salinas, Cobham and Diana), inoculated with Bremia and mock. The small RNA targets were also validated using PARE/degradome data derived from the same tissues.
Project description:Bolting is a key process in the growth and development of lettuce (Lactuca sativa L.). High temperature can induce earlier bolting which decreases in both quality and production of lettuce. However, knowledge underlying lettuce bolting is still lacking. To better understand the molecular basis of bolting, a comparative proteomics analysis was conducted on lettuce stems in the bolting period induced by high temperature (33 °C) compared with a control (20 °C) using iTRAQ-based proteomics, phenotypic measures, and biological verifications. High temperature induced lettuce bolting, while control temperature did not. Of the 6656 proteins identified, 758 proteins significantly altered their expression level induced by high-temperature relative to the control, of which 409 were up-regulated and 349 down-regulated. Proteins with abundance level change were mainly involved in photosynthesis, carbohydrate metabolism, stress response, hormone synthesis, and signal transduction. These differential proteins were mainly enriched in pathways associated with photosynthesis and tryptophan metabolism involving in auxin (IAA) biosynthesis. Among the differentially expressed proteins associated with photosynthesis and tryptophan metabolism were up-regulated. Moreover, in gibberellin (GA) biosynthesis pathway, 10 of main enzymes of P450 were up-regulated. Proteins related to SAUR and GRP, implicated in IAA and GA signal transduction were up-regulated, and the phosphorylation and ubiquitination related proteins regulating IAA and GA signal transduction were also induced. These findings indicate that a high temperature enhances the function of photosynthesis, IAA and GA synthesis and signal transduction to promote the process of bolting, which is in line with the physiology and transcription levels of IAA and GA metabolism. Our data provide a first comprehensive dataset for gaining novel understanding of the molecular basis underlying lettuce bolting induced by high temperature. It is potentially important for further functional analysis and genetic manipulation for molecular breeding to breed new cultivar of lettuce to restrain early bolting, which is vital for improving vegetable quality.
Project description:The draft genome of L. sativa (lettuce) cv. Tizian was sequenced in two Illumina sequencing runs, mate pair and shotgun. This entry contains the RAW sequencing data.
Project description:Lettuce (Lactuca sativa L.) is a highly perishable horticultural crop with a relatively short shelf life due to leaf senescence that limits its commercial value and contributes to food waste. Postharvest senescence varies with influences of both environmental and genetic factors. Preharvest genetic factors can be indicative of postharvest quality. Discovery of additional preharvest markers to assess lettuce shelf life is an important step towards increasing the efficiency of lettuce breeding efforts for improved shelf life. We selected and evaluated three romaine lettuces with variable shelf lives with the aim of identifying preharvest markers of lettuce postharvest shelf life. We evaluated leaf morphological characteristics for each of the three cultivars. To assess molecular indicators of shelf life, we used an RNA sequencing approach to construct transcriptomic profiles of two of the cultivars, a short shelf life (SSL) breeding line 60184 and a long shelf life (LSL) cultivar ‘Okeechobee’ at maturity. We identified 552 upregulated and 315 downregulated differentially expressed (DE) genes between the genotypes. We found that 27 % of the DE lettuce genes had an Arabidopsis thaliana ortholog characterized as senescence-associated, indicating that variable expression of senescence-associated genes (SAGs) could serve as a tool for preharvest markers of postharvest shelf life. Notably, we identified several SAGs and functional groupings with highly differential expression between the cultivars. This includes several jasmonate ZIM-domain (JAZ), jasmonic acid (JA) signaling genes, chlorophyll a-b binding (CAB) chloroplast-associated genes, and cell wall modification genes including pectate lyases (PL) and expansins (EXP). This study presented an innovative approach for identifying molecular markers for preharvest factors linked to postharvest traits for prolonged shelf. These genes could potentially be developed further as preharvest predictors of shelf life for lettuce breeding
Project description:Lettuce (Lactuca sativa L.) is one of the most important leafy vegetable that is consumed during its vegetative growth. The transition from vegetative to reproductive growth is induced by high temperature, which has significant economic effect on lettuce production. However, the progression of floral transition and the molecular regulation of bolting are largely unknown. Here we morphologically characterized the inflorescence development and functionally analyzed the FLOWERING LOCUS T (LsFT) gene during bolting regulation in lettuce. We described the 8 developmental stages during floral transition process. The expression of LsFT was negatively correlated with bolting in different lettuce varieties, and was promoted by heat treatment. Overexpression of LsFT could recover the late-flowering phenotype of ft-2 mutant. Knockdown of LsFT by RNA interference dramatically delayed bolting in lettuce, and failed to respond to high temperature. Therefore, this study dissects the process of inflorescence development and characterizes the role of LsFT in bolting regulation in lettuce.
Project description:This study utilized the HIT-ISOseq method for high-throughput sequencing of RNA isoforms across multiple lettuce samples, generating millions of long reads per PacBio Sequel II SMRT Cell. Analysis of six tissue types revealed tissue-specific gene expression and RNA isoforms, facilitating updates to the lettuce reference genome annotation with expanded functional annotations.
Project description:Small RNAs (21-24 nt) are pivotal regulators of gene expression that guide both transcriptional and post-transcriptional silencing mechanisms in diverse eukaryotes, including most if not all plants. MicroRNAs (miRNAs) and short interfering RNAs (siRNAs) are the two major types, both of which have a demonstrated and important role in plant development, stress responses and pathogen resistance. In this work, we used a deep sequencing approach (Sequencing-By-Synthesis, or SBS) to develop sequence resources of small RNAs from different Lactuca sativa tissues (including leaves, flowers, and fungus-infected leaves). The high depth of the resulting datasets enabled us to examine in detail critical small RNA features such as size distribution, tissue-specific regulation and sequence conservation between different organs in this species. We also developed database resources and a dedicated website (http://smallrna.udel.edu/) with computational tools for allowing other users to identify new miRNAs or siRNAs involved in specific regulatory pathways, verify the degree of conservation of these sequences in other plant species and map small RNAs on genes or larger regions of the genome under study. Small RNA libraries were derived from leaves and flowers of Lactuca sativa, cultivar Salinas, including leaves infected with the fungus Bremia lactucae, strain CA-III. Total RNA was isolated using TriReagent® (Molecular Research Center) and submitted to Illumina (Hayward, CA, http://www.illumina.com) for small RNA library construction using approaches described in (Lu et al., 2007) with minor modifications. The small RNA libraries were sequenced with the Sequencing-By-Synthesis (SBS) technology by Illumina. PERL scripts were designed to remove the adapter sequences and determine the abundance of each distinct small RNA. We thank Richard Michelmore and Oswaldo Ochoa for providing the plant material as well as Kan Nobuta for assistance with the computational methods.