Variation in Arabidopsis Flowering Time Associated with Cis-Regulatory Variation in CONSTANS

The onset of flowering, the change from vegetative to reproductive development, is a major life history transition in flowering plants. Recent work suggests that mutations in cis-regulatory mutations should play critical roles in the evolution of this (as well as other) important adaptive traits, but thus far there has been little evidence that directly links regulatory mutations to evolutionary change at the species level. While several genes have previously been shown to affect natural variation in flowering time in Arabidopsis thaliana, most either show protein-coding changes and/or are found at low frequency (\u3c5%). Here we identify and characterize natural variation in the cis-regulatory sequence in the transcription factor CONSTANS that underlies flowering time diversity in Arabidopsis. Mutation in this regulatory motif evolved recently and has spread to high frequency in Arabidopsis natural accessions, suggesting a role for these cis-regulatory changes in adaptive variation of flowering time

Developmental Reaction Norms for Water Stressed Seedlings of Succulent Cacti

Succulent cacti are remarkable plants with capabilities to withstand long periods of drought. However, their adult success is contingent on the early seedling stages, when plants are highly susceptible to the environment. To better understand their early coping strategies in a challenging environment, two developmental aspects (anatomy and morphology) in Polaskia chichipe and Echinocactus platyacanthus were studied in the context of developmental reaction norms under drought conditions. The morphology was evaluated using landmark based morphometrics and Principal Component Analysis, which gave three main trends of the variation in each species. The anatomy was quantified as number and area of xylem vessels. The quantitative relationship between morphology and anatomy in early stages of development, as a response to drought was revealed in these two species. Qualitatively, collapsible cells and collapsible parenchyma tissue were observed in seedlings of both species, more often in those subjected to water stress. These tissues were located inside the epidermis, resembling a web of collapsible-cell groups surrounding turgid cells, vascular bundles, and spanned across the pith. Occasionally the groups formed a continuum stretching from the epidermis towards the vasculature. Integrating the morphology and the anatomy in a developmental context as a response to environmental conditions provides a better understanding of the organism's dynamics, adaptation, and plasticity

Histological sections and schematic representations of <i>Echinocactus platycanthus</i> hypocotyls.

<p>Transversal sections were obtained 3–4 mm above the base of the shoot. <b>A</b>: Seedling of a Control treatment. <b>B</b> Seedling of a Stress treatment. <b>C</b> Vascular bundle area showing details of the collapsible cells and areas of collapsible tissue. <b>D</b>: Section of parenchyma showing turgid cells next to collapsed cells. <b>E–F</b>: Schematic representation of B,C respectively: turgid cells in green, collapsed cells in grey, xylem cells in red, and phloem cells in blue. <b>A–B</b>: Bright field microscopy; <b>C–D</b>: Phase contrast microscopy. White arrows show a turgid cell, black arrows show groups of collapsible cells. Scale bar 100 µm. CO: cortex; PI: pith; VB: vascular bundle.</p

Quantification of the morphology and the anatomy in cacti seedlings.

<p><b>A–C</b>: The morphology of <i>Polaskia chichipe</i> expressed as PC_Pol. <b>D–E</b>: The number and area of xylem vessels in <i>Polaskia chichipe</i>. <b>F–H</b>: The morphology of <i>Echinocactus platyacanthus</i> represented as PC_Ech. <b>I–J</b>: The number and area of vessels in <i>Echinocactus platyacanthus</i>. <b>D–E</b>,<b>I–J</b>: Significant PCs from the regression <i>y_i</i> = β_PC1+β_PC2+β_PC3+ε_i are highlighted. * p<0.5, *** p<0.0005. Error bars represent standard error. DAG: days after germination.</p

Seedlings of <i>Polaskia chichipe</i> and <i>Echinocactus platyacanthus</i> at three developmental stages and two water availability conditions.

<p>DAG: days after germination. Scale bar 1 mm for all images.</p

Morphometric analysis of seedling shape and size.

<p><b>A,B</b>: 30-point template to capture the shape of both <i>Polaskia chichipe</i> and <i>Echinocactus platyacanthus</i> seedlings. Open circles correspond to primary landmarks which are placed on recognizable features of the seedlings (base, cotyledonary areoles, and apex); filled circles correspond to secondary landmarks evenly spaced between primary landmarks. <b>C</b>: Example of the 30-point model template fitted onto a photographed seedling. <b>D</b>: Principal Component Analysis of <i>Polaskia chichipe</i> (PCA_Pol) and <i>Echinocactus platyacanthus</i> (PCA_Ech) seedlings. Mean shapes with and without procrustes for size are shown. SD: Standard deviation. PC1_Pol shows elongation of the apex with size effects.</p

A local tumor microenvironment acquired super-enhancer induces an oncogenic driver in colorectal carcinoma

The changes in super-enhancer (SE) landscape of cancers are mainly attributed to cell-intrinsic genomic alterations. Here, the authors perform epigenomic profiling on primary colorectal cancers (CRCs) and their matched normal tissues and show that local tumour microenvironment induces a SE activation and that its target, PDZK1IP1 promotes CRC growth