Project description:Chemical modifications to the tails of histone proteins act as gene regulators that play a pivotal role in adaptive responses to environmental stress. Determining the short and long term kinetics of histone marks is essential for understanding their functions in adaptation. We used Caenorhabditis elegans as a model organism to study the histone modification kinetics in response to environmental stress, taking advantage of their ability to live in both terrestrial and aquatic environments. We investigated the multigenerational genome-wide dynamics of five histone marks (H3K4me3, H3K27me3, H4K20me1, H3K36me1, and H3K9me3) by maintaining P0 animals on terrestrial (agar plates), F1 in aquatic cultures, and F2 back on terrestrial environments. We determined the distributions of histone marks in the gene promoter regions and found that H4K20me1, H3K36me1, and H3K9me3 showed up to eleven-fold differences in density, whereas H3K4me3 and H3K27me3 remained highly constant during adaptation from terrestrial to aquatic environments. Furthermore, we predicted that up to five combinations of histone marks can co-occupy single gene promoters and confirmed the colocalization of these histone marks by structured illumination microscopy. The co-occupancy increases with environment changes and different co-occupancy patterns contribute to variances in gene expressions and thereby presents a supporting evidence for the histone code hypothesis.
Project description:Rapid phenotypic changes in adaptive traits are crucial for organisms to thrive in changing environments. Alternanthera philoxeroides, originally a terrestrial plant from South America, has become an invasive weed in Asia, capable of colonizing both aquatic and terrestrial habitats. The mechanism by which this invasive habitat is rapidly achieved without genetic variation remains unknown. Here, we demonstrate that miRNA activity in A. philoxeroides plays a significant role in its high invasive capacity. Our results highlight that an intact miRNA pathway is essential for the survival of A.philoxeroides in aquatic habitats. We identified one key miRNA, Aph-miR162, that promotes rapid elongation of stem in aquatic environments. Upon water submergence, the levels of miR162 significantly increased in stems from 3 hours to 24 hours. TRV based VIGS-mediated knockdown of Aph-miR162 significantly disrupted stem elongation in water submergence condition, ultimately resulting in a failure of plants protruding from the water surface. Interestingly, miR162 was not up-regulated in the non-invasive sibling species Alternanthera pungens, which also originates from South America but has retained its original terrestrial habitats in Asia. More importantly, delivering the antisense RNA oligos complementary to Aph-miR162 via the nanoparticle method significantly impaired stem elongation upon water submergence, causing A. philoxeroides to wither after 2-3 weeks. Thus, our findings reveal that the miRNA pathway can drive rapid phenotypic variation, facilitating adaptation to aquatic environments. Importantly, miR162 has the potential as a bio-pesticide for controlling the invasive capacity of A. philoxeroides.
Project description:Study abstract: Axolotl salamanders (Ambystoma mexicanum) remain aquatic in their natural state, during which biomechanical forces on their diarthrodial limb joints are likely reduced relative to salamanders living on land. However, even as sexually mature adults, these amphibians can be induced to metamorphose into a weight-bearing terrestrial stage by environmental stress or the exogenous administration of thyroxine hormone. In some respects, this aquatic to terrestrial transition of axolotl salamanders through metamorphosis may model developmental and changing biomechanical skeletal forces in mammals during the prenatal to postnatal transition at birth and in the early postnatal period. To assess differences in the appendicular skeleton as a function of metamorphosis, anatomical and gene expression parameters were compared in skeletal tissues between aquatic and terrestrial axolotls that were the same age and genetically full siblings. The length of long bones and area of cuboidal bones in the appendicular skeleton, as well as the cellularity of cartilaginous and interzone tissues of femorotibial joints were generally higher in aquatic axolotls compared to their metamorphosed terrestrial siblings. A comparison of steady state mRNA transcripts encoding aggrecan core protein (ACAN), type II collagen (COL2A1), and growth and differentiation factor 5 (GDF5) in femorotibial cartilaginous and interzone tissues did not reveal any significant differences between aquatic and terrestrial axolotls. RNAseq samples: Total RNA was isolated from whole body tissue samples of Mexican axolotl salamanders (Ambystoma mexicanum) at the following developmental stages: Embryo at the tail bud stage, newly hatched larva, larva at the limb bud stage, juvenile at 8.5 centimeters, and adult using variations of guanidinium-based protocols. RNA quantity, purity, and integrity of both the individual samples and the resulting pool were determined with an Agilent 2100 Bioanalyzer using the Eukaryotic Total RNA nano series II analysis kit. The pooled RNA sample was poly-A selected and used for Illumina random priming directional library prep. Four lanes were sequenced only on one end providing single end reads and 4 lanes were sequenced at both ends giving paired-end reads. The library was sequenced on an Illumina HiSeq 2000 for 75bp reads producing 147,248,512 single end reads and 2 x 153,254,667 paired-end reads.
Project description:Land plant colonization was a pivotal event in the evolution of photosynthetic eukaryotes. The transition from aquatic to terrestrial environments required complex multisensory systems that enabled plants to perceive and integrate a broader range of environmental cues, such as light intensity and temperature. However, it remains unclear whether this ability was a pre-adaptation or an innovation during early plant terrestrialization. Here, we show that the aquatic streptophyte ancestor of land plants could integrate light and temperature through a complex regulatory network. A conserved regulatory nexus, comprising phytochromes and transcription factors, was active in the last common ancestor of land plants, allowing the first terrestrial colonizers to adapt and flourish on the harsh terrestrial surface of our planet. Thus, we propose that the multisensory integration that enables extant plants to achieve perceptual disambiguation and fine-tune growth in various ecological niches was a pre-adaptation encoded in the genomes of ancestral land plants.
Project description:Land plant colonization was a pivotal event in the evolution of photosynthetic eukaryotes. The transition from aquatic to terrestrial environments required complex multisensory systems that enabled plants to perceive and integrate a broader range of environmental cues, such as light intensity and temperature. However, it remains unclear whether this ability was a pre-adaptation or an innovation during early plant terrestrialization. Here, we show that the aquatic streptophyte ancestor of land plants could integrate light and temperature through a complex regulatory network. A conserved regulatory nexus, comprising phytochromes and transcription factors, was active in the last common ancestor of land plants, allowing the first terrestrial colonizers to adapt and flourish on the harsh terrestrial surface of our planet. Thus, we propose that the multisensory integration that enables extant plants to achieve perceptual disambiguation and fine-tune growth in various ecological niches was a pre-adaptation encoded in the genomes of ancestral land plants.