Phalaenopsis orchid miniaturization by overexpression of OsGA2ox6, a rice GA2-oxidase gene

Breeding of ornamental orchids with focus on Phalaenopsis: current approaches, tools, and challenges for this century

Ornamental orchid breeding programs have been conducted to develop commercially valuable cultivars with improved characteristics of commercial interest, such as size, flower color, pattern, shape, and resistance to pathogens. Conventional breeding, including sexual hybridization followed by selection of desirable characteristics in plants, has so far been the main method for ornamental breeding, but other techniques, including mutation induction by polyploidization and gamma irradiation, and biotechnological techniques, such as genetic transformation, have also been studied and used in ornamental breeding programs. Orchids are one of the most commercially important families in floriculture industry, having very particular reproductive biology characteristics and being a well-studied group of ornamentals in terms of genetic improvement. The present review focuses on the conventional and biotechnological techniques and approaches specially employed in breeding Phalaenopsis orchids, the genus with highest worldwide importance as an ornamental orchid, highlighting the main limitations and strengths of the approaches. Furthermore, new opportunities and future prospects for ornamental breeding in the CRISPR/Cas9 genome editing era are also discussed. We conclude that conventional hybridization remains the most used method to obtain new cultivars in orchids. However, the emergence of the first biotechnology-derived cultivars, as well as the new biotechnological tools available, such as CRISPR-Cas9, rekindled the full potential of biotechnology approaches and their importance for improve ornamental orchid breeding programs.

Plant Development and Crop Yield: The Role of Gibberellins

Gibberellins have been classically related to a few key developmental processes, thus being essential for the accurate unfolding of plant genetic programs. After more than a century of research, over one hundred different gibberellins have been described. There is a continuously increasing interest in gibberellins research because of their relevant role in the so-called "Green Revolution", as well as their current and possible applications in crop improvement. The functions attributed to gibberellins have been traditionally restricted to the regulation of plant stature, seed germination, and flowering. Nonetheless, research in the last years has shown that these functions extend to many other relevant processes. In this review, the current knowledge on gibberellins homeostasis and mode of action is briefly outlined, while specific attention is focused on the many different responses in which gibberellins take part. Thus, those genes and proteins identified as being involved in the regulation of gibberellin responses in model and non-model species are highlighted. The present review aims to provide a comprehensive picture of the state-of-the-art perception of gibberellins molecular biology and its effects on plant development. This picture might be helpful to enhance our current understanding of gibberellins biology and provide the know-how for the development of more accurate research and breeding programs.

Advances and prospects of orchid research and industrialization

Orchidaceae is one of the largest, most diverse families in angiosperms with significant ecological and economical values. Orchids have long fascinated scientists by their complex life histories, exquisite floral morphology and pollination syndromes that exhibit exclusive specializations, more than any other plants on Earth. These intrinsic factors together with human influences also make it a keystone group in biodiversity conservation. The advent of sequencing technologies and transgenic techniques represents a quantum leap in orchid research, enabling molecular approaches to be employed to resolve the historically interesting puzzles in orchid basic and applied biology. To date, 16 different orchid genomes covering four subfamilies (Apostasioideae, Vanilloideae, Epidendroideae, and Orchidoideae) have been released. These genome projects have given rise to massive data that greatly empowers the studies pertaining to key innovations and evolutionary mechanisms for the breadth of orchid species. The extensive exploration of transcriptomics, comparative genomics, and recent advances in gene engineering have linked important traits of orchids with a multiplicity of gene families and their regulating networks, providing great potential for genetic enhancement and improvement. In this review, we summarize the progress and achievement in fundamental research and industrialized application of orchids with a particular focus on molecular tools, and make future prospects of orchid molecular breeding and post-genomic research, providing a comprehensive assemblage of state of the art knowledge in orchid research and industrialization.

PavGA2ox-2L inhibits the plant growth and development interacting with PavDWARF in sweet cherry (Prunus avium L.)

Dwarf dense planting is helpful to improve the yield and quality of sweet cherry, which has enormous market demand. GA2oxs (GA oxidases) affect plant height, dormancy release, flower development, and seed germination by participating in the metabolic regulation and signal transduction of GA (Gibberellin). However, the research on GA2ox in sweet cherry is little and worthy of further investigation. Therefore, we identified the PavGA2ox-2L gene from sweet cherry, close to PynGA2ox-2 from Prunus yedoensis var. Nudiflora. The phylogenetic analysis indicated conserved functions with these evolutionarily closer GA2ox subfamily genes. Subcellular localization forecast analysis indicated that PavGA2ox-2L was localized in the nucleus or cytoplasm. The expression levels of PavGA2ox-2L were higher in winter, indicating that PavGA2ox-2L promoted maintained flower bud dormancy. The expression levels of PavGA2ox-2L were significantly increased after GA₄₊₇ treatment while decreased after GR24 (a synthetic analog of SLs (Strigolactones)) or TIS108 (a triazole-type SL-biosynthesis inhibitor) treatments. Over-expression of PavGA2ox-2L resulted in decreased plant height, delayed flowering time, and low seed germination rate in Arabidopsis thaliana. Furthermore, the interaction between PavGA2ox-2L and PavDWARF was verified by Y2H and BiFC assays. In the current investigation, PavGA2ox-2L functions as a GA metabolic gene that promotes dwarf dense planting, delays flowering time, and inhibits seed germination. In addition, it also participates in regulating plant growth and development through the interaction with the critical negative regulator PavDWARF of Gibberellin. These results will help us better explore the molecular mechanism of GA2ox-mediated dwarf and late-maturing varieties for fruit trees.

Polyploidization in Orchids: From Cellular Changes to Breeding Applications

Polyploidy occurs naturally in plants through cell division errors or can artificially be induced by antimitotic agents and has ecological effects on species adaptation, evolution, and development. In agriculture, polyploidy provides economically improved cultivars. Furthermore, the artificial induction of polyploids increases the frequency; thus, it accelerates obtaining polyploid plants used in breeding programs. This is the reason for its use in developing many crops of economic interest, as is the case of orchids in the flower market. Polyploidy in ornamental plants is mainly associated with flowers of larger size, fragrance, and more intense coloring when compared to naturally diploid plants. Currently, orchids represent the largest flower market worldwide; thus, breeding programs aim to obtain flowers with the larger size, durability, intense colors, and resistance to pathogens. Furthermore, orchid hybridization with polyploidy induction has been used to produce improved hybrid cultivars. Thus, the objective of this review was to compile information regarding the natural occurrence, importance, and methods of induction of polyploidy in orchids. The study also summarizes the significance of polyploids and techniques associated with artificially inducing polyploidy in different orchids of commercial relevance.

OsBIC1 Directly Interacts with OsCRYs to Regulate Leaf Sheath Length through Mediating GA-Responsive Pathway

Cryptochrome 1 and 2 (CRY1 and CRY2) are blue light receptors involved in the regulation of hypocotyl elongation, cotyledon expansion, and flowering time in Arabidopsisthaliana. Two cryptochrome-interacting proteins, Blue-light Inhibitor of Cryptochrome 1 and 2 (BIC1 and BIC2), have been found in Arabidopsis. BIC1 plays critical roles in suppressing the physiological activities of CRY2, which include the blue light-dependent dimerization, phosphorylation, photobody formation, and degradation process, but the functional characterization of BIC protein in other crops has not yet been performed. To investigate the function of BIC protein in rice (Oryza sativa), two homologous genes of Arabidopsis BIC1 and BIC2, namely OsBIC1 and OsBIC2 (OsBICs), were identified. The overexpression of OsBIC1 and OsBIC2 led to increased leaf sheath length, whereas mutations in OsBIC1 displayed shorter leaf sheath in a blue light intensity-dependent manner. OsBIC1 regulated blue light-induced leaf sheath elongation through direct interaction with OsCRY1a, OsCRY1b, and OsCRY2 (OsCRYs). Longitudinal sections of the second leaf sheath demonstrated that OsBIC1 and OsCRYs controlled leaf sheath length by influencing the ratio of epidermal cells with different lengths. RNA-sequencing (RNA-seq) and quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) analysis further proved that OsBIC1 and OsCRYs regulated similar transcriptome changes in regulating Gibberellic Acids (GA)-responsive pathway. Taken together, these results suggested that OsBIC1 and OsCRYs worked together to regulate epidermal cell elongation and control blue light-induced leaf sheath elongation through the GA-responsive pathway.