Sequences surrounding the transcription initiation site of the Arabidopsis enoyl-acyl carrier protein reductase gene control seed expression in transgenic tobacco.

The NADH-specific enoyl-acyl carrier protein (ACP) reductase, which catalyses the last reducing step during the fatty acid biosynthesis cycle, is encoded in Arabidopsis thaliana encoded by a single housekeeping gene (ENRA) which is differentially expressed during plant development. To identify elements involved in its tissue-specific transcriptional control, a fragment comprising the 1470 bp region directly upstream of the ATG start codon of the ENR-A gene was fused to the uidA (GUS) reporter gene and analysed in transgenic Nicotiana tabacum plants. GUS activity found during development of the transgenic plants was similar to endogenous ENR protein levels found in both tobacco and Arabidopsis plants, except for developing flowers. In floral tissue the promoter fragment showed very little activity in contrast to the relatively high level of endogenous ENR expression. Successive deletions from the 5' and 3' regions of the promoter fragment revealed the presence of at least three elements which control GUS expression in different stages of development in the transgenic tobacco plants. First, expression in young developing leaves required both the presence of sequences between -329 to -201 relative to the transcription start and part of the untranslated leader comprising the first intron. Second, root-specific GUS expression was still observed after deletion of the 5'-upstream sequences up to 19 bp of the transcription initiation site. Further, the additional removal of the intron from the untranslated leader increased root-specific expression by ca. 4- to 5-fold. Third, high expression in seeds was still observed with the minimal upstream promoter segment of 19 bp. This seed expression level was found to be independent of the presence or absence of the intron in the untranslated leader. Finally, 3' deletion of the leader sequence up to 17 bp of the transcription start greatly impaired GUS activity during all stages of plant development, suggesting that the deleted sequence of the leader either functions as an enhancer for transcription initiation or stabilizes the mRNA

Capturing Arabidopsis Root Architecture Dynamics with root-fit Reveals Diversity in Responses to Salinity

The plant root is the first organ to encounter salinity stress, but the effect of salinity on root system architecture (RSA) remains elusive. Both the reduction in main root (MR) elongation and the redistribution of the root mass between MRs and lateral roots (LRs) are likely to play crucial roles in water extraction efficiency and ion exclusion. To establish which RSA parameters are responsive to salt stress, we performed a detailed time course experiment in which Arabidopsis (Arabidopsis thaliana) seedlings were grown on agar plates under different salt stress conditions. We captured RSA dynamics with quadratic growth functions (root-fit) and summarized the salt-induced differences in RSA dynamics in three growth parameters: MR elongation, average LR elongation, and increase in number of LRs. In the ecotype Columbia-0 accession of Arabidopsis, salt stress affected MR elongation more severely than LR elongation and an increase in LRs, leading to a significantly altered RSA. By quantifying RSA dynamics of 31 different Arabidopsis accessions in control and mild salt stress conditions, different strategies for regulation of MR and LR meristems and root branching were revealed. Different RSA strategies partially correlated with natural variation in abscisic acid sensitivity and different Na(+)/K(+) ratios in shoots of seedlings grown under mild salt stress. Applying root-fit to describe the dynamics of RSA allowed us to uncover the natural diversity in root morphology and cluster it into four response types that otherwise would have been overlooked

A mixed-model QTL analysis for salt tolerance in seedlings of crop-wild hybrids of lettuce

Cultivated lettuce is more sensitive to salinity stress than its wild progenitor species potentially due to differences in root architecture and/or differential uptake and accumulation of sodium. We have identified quantitative trait locis (QTLs) associated with salt-induced changes in root system architecture (RSA) and ion accumulation using a recombinant inbred line population derived from a cross between cultivated lettuce (Lactuca sativa ‘Salinas’) and wild lettuce (L. serriola). Components of RSA were quantified by replicated measurements of seedling growth on vertical agar plates containing different concentrations of NaCl in a controlled growth chamber environment. Accumulation of sodium and potassium ions was measured in replicates of greenhouse-grown plants watered with 100 mM NaCl water. A total of 14 QTLs were identified using multi-trait linkage analysis, including three major QTLs associated with general root development, root growth in salt stress condition, and ion accumulation. The three major QTLs, qRC9.1, qRS2.1, and qLS7.2, were linked with markers E35/M59-F-425, LE9050, and LE1053, respectively. This study provides regions of lettuce genome contributing to salt-induced changes in RSA and ion accumulation. Future fine-mapping of major QTLs will identify candidate genes underlying salt stress tolerance in cultivated lettuce

Genetic Components of Root Architecture Remodeling in Response to Salt Stress

Salinity of the soil is highly detrimental to plant growth. Plants respond by a redistribution of root mass between main and lateral roots, yet the genetic machinery underlying this process is still largely unknown. Here, we describe the natural variation among 347 Arabidopsis thaliana accessions in root system architecture (RSA) and identify the traits with highest natural variation in their response to salt. Salt-induced changes in RSA were associated with 100 genetic loci using genome-wide association studies. Two candidate loci associated with lateral root development were validated and further investigated. Changes in CYP79B2 expression in salt stress positively correlated with lateral root development in accessions, and cyp79b2 cyp79b3 double mutants developed fewer and shorter lateral roots under salt stress, but not in control conditions. By contrast, high HKT1 expression in the root repressed lateral root development, which could be partially rescued by addition of potassium. The collected data and multivariate analysis of multiple RSA traits, available through the Salt_NV_Root App, capture root responses to salinity. Together, our results provide a better understanding of effective RSA remodeling responses, and the genetic components involved, for plant performance in stress conditions

Egg length of Anastrepha obliqua Macquart (Diptera, Tephritidae) according to oviposition rate and maternal age

The length of the entire egg, micropile and vitellus regions of Anastrepha obliqua Macquart, 1835 were measured during all opposition period. Obtained values were compared among them and with oviposition rate. The smallest eggs were produced during the first 35 oviposition days, period where the highest oviposition rate occured. The decrease in egg length was found to be due to a descrease in the vitellus region. Micropile length was found to be pratically constant throughout oviposition. Furthermore, no relationship between maternal age and length was detectable