The complete chloroplast genome of Goodyera yunnanensis Schltr.

The family Orchidaceae is renowned for its extensive diversity. Within this family, the genus Goodyera R. Br. is classified under the subtribe Goodyerinae, comprising approximately 99 species. In this study, a species Goodyera yunnanensis Schltr., its plastid genome was characterized. The plastid genome of G. yunnanensis is 146,197 bp in size and exhibits a typical quadripartite structure with a pair of inverted repeat regions (IRs) of 25,611 bp, a large single-copy region (LSC) of 81,300 bp and a small single-copy region (SSC) of 13,675 bp. A total of 126 genes were identified, containing 80 protein-coding genes, 38 tRNA genes and 8 rRNA genes. The overall GC content is 37.2%, with corresponding values of 43.3%, 34.7% and 29.1% in IR, LSC and SSC regions, respectively. Forty-seven simple sequence repeats (SSRs) are found in G. yunnanensis plastome, and the frequency of mononucleotide repeats is significantly higher than other repeat types. Phylogenetic analysis indicates that Goodyera is resolved into four clades. G. yunnanensis belongs to the monophyletic clade A, and its phylogenetic position can be reasonably supported by morphological and molecular data.

Integrated Transcriptomic and Proteomic Analyses Uncover the Regulatory Mechanisms of Myricaria laxiflora Under Flooding Stress.

Flooding is one of the major environmental stresses that severely influence plant survival and development. However, the regulatory mechanisms underlying flooding stress remain largely unknown in Myricaria laxiflora, an endangered plant mainly distributed in the flood zone of the Yangtze River, China. In this work, transcriptome and proteome were performed in parallel in roots of M. laxiflora during nine time-points under the flooding and post-flooding recovery treatments. Overall, highly dynamic and stage-specific expression profiles of genes/proteins were observed during flooding and post-flooding recovery treatment. Genes related to auxin, cell wall, calcium signaling, and MAP kinase signaling were greatly down-regulated exclusively at the transcriptomic level during the early stages of flooding. Glycolysis and major CHO metabolism genes, which were regulated at the transcriptomic and/or proteomic levels with low expression correlations, mainly functioned during the late stages of flooding. Genes involved in reactive oxygen species (ROS) scavenging, mitochondrial metabolism, and development were also regulated exclusively at the transcriptomic level, but their expression levels were highly up-regulated upon post-flooding recovery. Moreover, the comprehensive expression profiles of genes/proteins related to redox, hormones, and transcriptional factors were also investigated. Finally, the regulatory networks of M. laxiflora in response to flooding and post-flooding recovery were discussed. The findings deepen our understanding of the molecular mechanisms of flooding stress and shed light on the genes and pathways for the preservation of M. laxiflora and other endangered plants in the flood zone.

Hot Deformation Behavior and Workability of In Situ TiB2/7050Al Composites Fabricated by Powder Metallurgy.

Isothermal compression tests of in situ TiB2/7050Al composites fabricated by powder metallurgy were performed at 300-460 °C with the strain rate varying from 0.001 s-1 to 1 s-1. The Arrhenius constitutive equation and hot processing map of composites were established, presenting excellent hot workability with low activation energies and broad processing windows. Dramatic discontinuous/continuous dynamic recrystallization (DDRX/CDRX) and grain boundary sliding (GBS) take place in composites during deformation, depending on the Zener-Hollomon parameter (Z) values. It was found that initially uniform TiB2 particles and fine grain structures are beneficial to the DDRX, which is the major softening mechanism in composites at high Z values. With the Z value decreasing, dynamic recovery and CDRX around particles are enhanced, preventing the occurrence of DDRX. In addition, fine grain structures in composites are stable at elevated temperature thanks to the pinning of dense nanoparticles, which triggers the occurrence of GBS and ensures good workability at low Z values.

Identification and characterization of PaGL1-like genes from Platanus acerifolia related to the regulation of trichomes.

KEY MESSAGE: Two PaGL1-like genes were identified in London plane and functional in Arabidopsis, moreover, may play an important role in the regulation of trichome development in London plane. Trichome development is governed by a complex regulatory network. In Arabidopsis, subgroup 15 of the R2R3 MYB transcription factor family, which includes GLABRA1 (GL1), is involved in trichome development. In this study, we isolated and characterized two PaGL1-like genes from London plane (Platanus acerifolia). Sequence alignment and phylogenetic analysis indicated that these PaGL1-like genes are homologous to AtGL1. Quantitative real-time PCR (qRT-PCR) analysis showed that PaGL1-like1 was expressed in all of the tested organs taken from adult London plane trees, including trichomes, petioles after trichome removal, stems after trichome removal, and leaves after trichome removal, and also in the roots, cotyledons, hypocotyls and true leaves of seedlings. By contrast, the PaGL1-like2 was expressed only in the trichomes and leaves after trichome removal from adult trees, and in the cotyledons and true leaves of seedlings. Overexpression of PaGL1-like genes caused trichome abortion when transferred into wild type Arabidopsis and promoted trichome formation in the gl1 mutant. The expression profiles of some trichome-related genes were changed in transgenic Arabidopsis lines, and yeast two-hybrid analysis indicated that PaGL1-like proteins can directly interact with trichome-related bHLH proteins from both P. acerifolia and Arabidopsis. These results suggest that PaGL1-like genes are functional in Arabidopsis and may play an important role in the regulation of trichome development in London plane.

PaMYB82 from Platanus acerifolia regulates trichome development in transgenic Arabidopsis.

The control of epidermal cell fate is an elaborate molecular process mediated by the TTG1-bHLH-MYB regulatory complex. In this study, we isolated PaMYB82 from London plane. PaMYB82 was revealed to be a nuclear-localized transcription activator and was found to be expressed ubiquitously in the tissues of roots, stems, leaves, cotyledons and hypocotyls. Expression of the PaMYB82 gene under the control of the viral CaMV35S promoter caused a nearly glabrous phenotype in wild type Arabidopsis and can partially rescue the gl1 mutant phenotype. Protein interaction analysis revealed that PaMYB82 physically interacts with PaGL3 and itself, in addition, PaMYB82 could interact with trichome related bHLH transcription factors AtGL3, AtEGL3 and AtMYC1. Expression levels of AtGL2, AtTTG2 and several R3 MYB genes were greatly increased in 35S::PaMYB82 lines. The expression of AtMYB23 was reduced in 35S::PaMYB82 transgenic lines, whereas, expression levels of AtGL1 remained unchanged indicating that differences in the transcriptional regulation of AtMYB23 and AtGL1 during trichome development. Together, the data presented here indicate that PaMYB82 encodes a functional R2R3 MYB transcription factor which can control the initiation of Arabidopsis trichome development.