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Long terminal repeat retrotransposons (LTR retrotransposons) are the most abundant group of mobile genetic elements in eukaryotic genomes and are essential in organizing genomic architecture and phenotypic variations. The diverse families of retrotransposons are related to retroviruses. As retrotransposable elements are dispersed and ubiquitous, their “copy-out and paste-in” life cycle of replicative transposition leads to new genome insertions without the excision of the original element. The overall structure of retrotransposons and the domains responsible for the various phases of their replication is highly conserved in all eukaryotes. The two major superfamilies of LTR retrotransposons, Ty1/Copia and Ty3/Gypsy, are distinguished and dispersed across the chromosomes of higher plants. Members of these superfamilies can increase in copy number and are often activated by various biotic and abiotic stresses due to retrotransposition bursts. LTR retrotransposons are important drivers of species diversity and exhibit great variety in structure, size, and mechanisms of transposition, making them important putative actors in genome evolution. Additionally, LTR retrotransposons influence the gene expression patterns of adjacent genes by modulating potential small interfering RNA (siRNA) and RNA-directed DNA methylation (RdDM) pathways. Furthermore, comparative and evolutionary analysis of the most important crop genome sequences and advanced technologies have elucidated the epigenetics and structural and functional modifications driven by LTR retrotransposon during speciation. However, mechanistic insights into LTR retrotransposons remain obscure in plant development due to a lack of advancement in high throughput technologies. In this review, we focus on the key role of LTR retrotransposons response in plants during heat stress, the role of centromeric LTR retrotransposons, and the role of LTR retrotransposon markers in genome expression and evolution.

Mariner-like elements (MLEs) are promising tools for gene cloning, gene expression, and gene tagging. We have characterized two MLE transposons from moso bamboo, Ppmar1 and Ppmar2. Ppmar2, is smaller in size and has higher natural activities, thus making it a more potential genomic tool compared to Ppmar1. Using a two-component system consisting of a transposase expression cassette and a non-autonomous transposon cotransformed in yeast, we investigated the transposition activity of Ppmar2 and created hyperactive transposases. Five out of 19 amino acid mutations in Ppmar2 outperformed the wild-type in terms of catalytic activities, especially with the S347R mutant having 6.7-fold higher transposition activity. Moreover, 36 yeast mutants with single-gene deletion were chosen to screen the effects of the host factors on Ppmar2NA transposition. Compared to the control strain (his3Δ), the mobility of Ppmar2 was greatly increased in 9 mutants and dramatically decreased in 7 mutants. The transposition ability in the efm1Δ mutant was 15-fold higher than in the control, while it was lowered to 1/66 in the rtt10Δ mutant. Transcriptomic analysis exhibited that EFM1 defection led to the significantly impaired DDR2, HSP70 expression and dramatically boosted JEN1 expression, whereas RTT10 defection resulted in significantly suppressed expression of UTP20, RPA190 and RRP5. Protein methylation, chromatin and RNA transcription may affect the Ppmar2NA transposition efficiency in yeast. Overall, the findings provided evidence for transposition regulation and offered an alternative genomic tool for moso bamboo and other plants.

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Vanda malipoensis L.H.Zou, J.X.Huang & Z.J.Liu, sp. nov. (NJDZ������������) (Figs. 3, 4). Diagnosis: This new species is related to V. christensoniana and V. nana. It differs from V. christensoniana by having 4���6 cm long inflorescences with sparse flowers that are almost 50% smaller with a shorter column (2.5���3.0 mm) and spur (7.0��� 7.5 mm) and caudiculate pollinia sitting in a dorsal position on the stipe. It can be distinguished from V. nana by its longer inflorescence, widely opening and larger flowers and erect lateral lobes of the lip. Type:������ China. Yunnan (������): Malipo (NJDZ ���), epiphytic on tree trunks in forests; 30 June 2014, Liu 6644 (holotype: NOCC!). Epiphytic herbs with erect stems to 50���150 mm, 3���5 mm in diameter. Leaves distichous, slightly V-shaped in cross section, green, 100���200 �� 5���7 mm, apex truncate and unequally 3���4-dentate, base sheathing and jointed. Inflorescences axillary, ascending, 40���60 mm long with 7���12 flowers per inflorescence; floral bracts ovate-triangular, 1.0��� 1.5 mm. Flowers white, tinged with pink, opening widely; pedicel and ovary 10���12 mm. Dorsal sepal elliptic, 8.0���9.0 �� 3.5���4.0 mm, obtuse; lateral sepals obliquely elliptic, 7.5���8.5 �� 4.0��� 4.5 mm, apex acute; petals obovate-elliptic, 8.0���9.0 �� 3.0��� 3.5 mm, acute; lip spurred, trilobed, spotted with purple on the entrance of spur; lateral lobes subtriangular, erect, 1.5���1.8 �� 0.8���1.0 mm; midlobe ligulate, 3.0���3.5 �� 1.2���1.5 mm, obtuse, with an emarginate basal callus; spur clavatecylindrical, 7.0��� 7.5 mm, contracted at middle, apex dilated. Column 2.5���3.0 mm, foot absent; rostellum emarginate, lobes sharp; anther cap dark purple; pollina 2, globose, waxy, caudiculate, each cleft on the apex, attached by the stipe to a viscidium. Flowering period:���June. Distribution and habitat:��� Vanda malipoensis is epiphytic on tree trunks in forests, known so far only from Malipo, Yunnan Province, China. Etymology:���The species epithet refers to the locality where this new species has been found so far. Conservation status:���Within 10 km-radius around the type locality, our survey crew searched 18 locations for V. malipoensis. Only two of the 18 locations were found to contain the new species. Including the type locality, nine, seven and six individuals were found, respectively. The three sites were more than 2 km apart from each other. Using the World Conservation Union Red List Categories and Criteria (IUCN, 2012), V. malipoensis should be preliminarily treated as critically endangered (CR B 2ab)., Published as part of Zou, Long-Hai, Liu, Zhong-Jian & Huang, Jiu-Xiang, 2014, Vanda malipoensis, a new species of Vanda (Orchidaceae: Epidendroideae; Vandeae) from China: evidence from morphological and molecular phylogenetic analyses, pp. 87-96 in Phytotaxa 186 (2) on pages 94-95, DOI: 10.11646/phytotaxa.186.2.3, http://zenodo.org/record/5146967, {"references":["IUCN. (2012) IUCN Red List categories and criteria, version 3.1. Second edition. Gland, Switzerland and Cambridge, UK."]}