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NAC transcription factors play critical roles in xylem secondary development and in regulation of stress response in plants. NAC proteins related to secondary cell wall development were recently identified and characterized in

Teak is known as one of the world’s premier hardwood tree species. However, despite the commercial interest and the large number of scientific investigations, comprehensive understanding on the genetic, molecular, and biochemical processes of this species has only recently begun to be explored. Functional genomics is the field of molecular biology that utilizes widespread combination of genetic information (e.g., enhancer DNA and non-coding RNA) and genome modification technologies to understand interactions between genes and functional regulatory elements. These technologies have emerged as a novel way to understand plant gene functions. Importance of teak has propelled various studies on transcriptomics and molecular genetics. In the last decade, transcriptomics of T. grandis of secondary wood, vegetative to flowering transition stage, and seedlings under water stress were documented. These transcriptomic studies have led to identification of genes involved in xylogenesis, production of secondary metabolites, flower formation, and drought stress. Teak transformation has not been fully achieved, but model plants are currently being used for studying several teak genes. Thus, future of functional genomics of teak is promising, particularly when the existing transcriptome data are used for wide range of analysis.

NAC transcription factors play critical roles in xylem secondary development and in regulation of stress response in plants. NAC proteins related to secondary cell wall development were recently identified and characterized inTectona grandis(teak), one of the hardwood trees of highest economic importance in the world. In this work, we characterized the novelTgNAC01gene, which is involved in signaling pathways that mediate teak response to stress. Abscisic acid (ABA) increasesTgNAC01expression in teak plants. Therefore, this gene may have a role in signaling events that mediate ABA-dependent osmotic stress responsive in this plant species. Stable expression in tobacco plants showed that the TgNAC01 protein is localized in the cell nucleus. Overexpression ofTgNAC01in two out three independent transgenic tobacco lines resulted in increased growth, leaf senescence and salt tolerance compared to wild type (WT) plants. Moreover, the stress tolerance of transgenic plants was affected by levels ofTgNAC01gene expression. Water potential, gas exchange and chlorophyll fluorescence were used to determine salt stress tolerance. The 35S:TgNAC01-6 line under 300 mM NaCl stress responded with a significant increase in photosynthesis rate, stomatal conductance, transpiration and carboxylation efficiency, but lower water potential compared to WT plants. The data indicate that theTgNAC01transcription factor acts as a transcriptional activator of the ABA-mediated regulation and induces leaf senescence.

NAC proteins are one of the largest families of plant-specific transcription factors (TFs). They regulate diverse complex biological processes, including secondary xylem differentiation and wood formation. Recent genomic and transcriptomic studies of Tectona grandis L.f. (teak), one of the most valuable hardwood trees in the world, have allowed identification and analysis of developmental genes. In the present work, T. grandis NAC genes were identified and analyzed regarding to their evolution and expression profile during wood formation. We analyzed the recently published T. grandis genome, and identified 130 NAC proteins that are coded by 107 gene loci. These proteins were classified into 23 clades of the NAC family, together with Populus, Eucalyptus, and Arabidopsis. Data on transcript expression revealed specific temporal and spatial expression patterns for the majority of teak NAC genes. RT-PCR indicated expression of VND genes (Tg11g04450-VND2 and Tg15g08390-VND4) related to secondary cell wall formation in xylem vessels of 16-year-old juvenile trees. Our findings open a way to further understanding of NAC transcription factor genes in T. grandis wood biosynthesis, while they are potentially useful for future studies aiming to improve biomass and wood quality using biotechnological approaches.

Drought stress is an increasingly common and worrying phenomenon because it causes a loss of production in both agriculture and forestry. Teak is a tropical tree which needs alternating rainy and dry seasons to produce high-quality wood. However, a robust understanding about the physiological characteristics and genes related to drought stress in this species is lacking. Consequently, after applying moderate and severe drought stress to teak seedlings, an infrared gas analyzer (IRGA) was used to measure different parameters in the leaves. Additionally, using the root transcriptome allowed finding and analyzing the expression of several drought-related genes. As a result, in both water deficit treatments a reduction in photosynthesis, transpiration, stomatal conductance and leaf relative water content was found. As well, an increase in free proline levels and intrinsic water use efficiency was found when compared to the control treatment. Furthermore, 977 transcripts from the root contigs showed functional annotation related to drought stress, and of these, TgTPS1, TgDREB1, TgAREB1 and TgPIP1 were selected. The expression analysis of those genes along with TgHSP1, TgHSP2, TgHSP3 and TgBI (other stress-related genes) showed that with moderate treatment, TgTPS1, TgDREB1, TgAREB1, TgPIP1, TgHSP3 and TgBI genes had higher expression than the control treatment, but with severe treatment only TgTPS1 and TgDREB1 showed higher expression than the control treatment. At the end, a schematic model for the physiological and molecular strategies under drought stress in teak from this study is provided. In conclusion, these physiological and biochemical adjustments in leaves and genetic changes in roots under severe and prolonged water shortage situations can be a limiting factor for teak plantlets’ growth. Further studies of those genes under different biotic and abiotic stress treatments are needed.

The passion fruit (Passiflora cincinnata Mast.) is a perennial and drought resistant species that represents a new alternative crop for small farmers in rainfed conditions. This study aimed to evaluate the vegetative and physiological development of passion fruit plants derived from two propagation methods and grown at varied planting spacing. The experiment was conducted from January to June of 2012, in the Universidade Estadual do Sudoeste da Bahia (State University from Southwestern Bahia), in Brazil. It was carried out in a randomized block design under a 2 x 3 factorial scheme, which consisted of two propagation methods (cutting and seeds) and three planting spacing distances within a row (1.5; 3.0 and 4.0 m), however, at same distance between rows (3.0 m), with four replicates and four plants per plot. Cuttings and seeds were sampled from adult plants pre-selected in native areas from Vitória da Conquista - BA, Brazil. Growth (stem diameter and leaf area) and physiological parameters (leaf chlorophyll content, leaf water potential before dawn, relative water content and leaf gas exchange) were assessed on the 90th, 120th and 150th day after transplanting of seedlings into the field (DAT). Based on our results, we concluded that despite plants propagated via cuttings showed most favorable water status, vegetative growth and photosynthetic capacity were lower whether compared to plants obtained from seeds. RESUMO: O maracujá-do-mato (Passiflora cincinnata Mast.) é uma espécie perene, resistente à seca, podendo representar uma nova alternativa de cultivo para o pequeno agricultor em condições de sequeiro. O presente trabalho teve como objetivo avaliar o desenvolvimento vegetativo e fisiológico de plantas de maracujá-do-mato, sob diferentes condições de propagação e espaçamentos. O experimento foi conduzido no período de janeiro a junho de 2012, na Universidade Estadual do Sudoeste da Bahia, com o delineamento em blocos casualizados, em esquema fatorial 2 x 3, constituído por dois métodos de propagação e três espaçamentos de plantio na linha (3,0 x 1,5; 3,0 x 3,0 e 3,0x 4,0 m) permanecendo constantes as distâncias entre as linhas de plantio de 3,0 m, com quatro repetições e quatro plantas por parcela. As estacas e sementes foram coletadas de plantas adultas selecionadas em áreas nativas de Vitória da Conquista-BA. Foram realizadas avaliações de crescimento (diâmetro do caule e área foliar) e fisiológicas (teor de clorofila na folha, potencial hídrico foliar antemanhã, teor relativo de água e trocas gasosas foliares) aos 90, 120 e 150 dias após transplantio das mudas no campo (DAT). Nas condições em que o trabalho foi conduzido conclui-se que apesar da manutenção de status hídrico mais favorável das plantas propagadas via estaquia, o desenvolvimento vegetativo e a capacidade fotossintética são reduzidas quando comparadas aos de plantas obtidas por meio de sementes.

NAC proteins are one of the largest families of plant-specific transcription factors (TFs). They regulate diverse complex biological processes, including secondary xylem differentiation and wood formation. Recent genomic and transcriptomic studies of Tectona grandis L.f. (teak), one of the most valuable hardwood trees in the world, have allowed identification and analysis of developmental genes. In the present work, T. grandis NAC genes were identified and analyzed regarding to their evolution and expression profile during wood formation. We analyzed the recently published T. grandis genome, and identified 130 NAC proteins that are coded by 107 gene loci. These proteins were classified into 23 clades of the NAC family, together with Populus, Eucalyptus, and Arabidopsis. Data on transcript expression revealed specific temporal and spatial expression patterns for the majority of teak NAC genes. RT-PCR indicated expression of VND genes (Tg11g04450-VND2 and Tg15g08390-VND4) related to secondary cell wall formation in xylem vessels of 16-year-old juvenile trees. Our findings open a way to further understanding of NAC transcription factor genes in T. grandis wood biosynthesis, while they are potentially useful for future studies aiming to improve biomass and wood quality using biotechnological approaches.

The purpose of this study was to evaluate the effects of light restriction on the growth of benghal dayflower (Commelina benghalensis). The experiment was conducted in pots under full sunlight and with 18.5, 30, 40, 50, 60 and 70% artificial light restriction treatments. Plant growth was evaluated up to 90 days after planting (DAP), and mathematical models of the major shoot length, internode length, individual area of the first leaf completely expanded, number of leaves and shoot and root dry mass weights were established depending on increasing light restriction levels. The elevation of the light gradient promoted reductions in the number of leaves and fasciculate root dry mass weight. Light restriction did not induce alterations in the plasticity of performance (alterations in total biomass accumulation) of the C. benghalensis plants, the stability of which was related to an integration of the expected morphological, anatomical and physiological adjustments, constituting in a strong evidence of shading tolerance.