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Macaubest: a comprehensive transcriptome of macaúba palm (Acrocomia aculeata)

terça-feira, março 26, 2019


 A. Adult plant of macaúba palm. B. Bunch of fruits; C. Ripe fruit in detail; fruit without epicarp (yellow mesocarp); D. Open inflorescence; E. Detail of inflorescence, with female flowers located in the basal region and male flowers in the apical region. (COLOMBO et al., 2018)

Author: Bazzo, Bárbara Regina

Abstract: The macaúba palm (Acrocomia aculeata) is a native and widespread palm tree, being present mainly in Brazilian Cerrado. It is considered an alternative oil-feedstock crop since it has high productivity, high oil content, high-quality oil, as well as it is possible to plant in drought areas. Consequently, molecular biology and genetic diversity studies may provide the basis for a successful breeding program. Therefore, this study aimed to build a macaúba palm gene bank and develop molecular markers for genetic diversity studies, marker-assisted selection, and population mapping. 

Moreover, the studies investigated possible differences between the macaúba pam and African oil palm, which are genetically close but with different edaphoclimatic requirements. For this, the RNA was extracted from the root, bulb, leaf, flower (female and male), and mesocarp of mature fruits. In the first experiment, De novo transcriptome assembly permitted to identify 34.293 transcripts of macaúba palm in all the libraries, gathered in a single reference. Gene expression analysis showed eight transcripts expressed only in fruit tissues, two in leaf tissue, eight in bulb tissue, five in female flowers, 14 in male flowers, 8053 in root and none in leaf sheath tissue. Furthermore, we observed 341 root-specific transcripts with high expression level. In addition, family turnover analysis between macaúba palm and African oil palm showed that macaúba has 24 expanded gene families, 11 families have at least one root-specific transcript and six families are exclusive of macaúba palm. 

Most transcripts were similarly to transduction proteins related to abiotic and biotic stresses responses, such as kinases, transcription factors, Ca2+-binding proteins. The data suggest a possible regulation of signal transduction in response to many stresses. In the second experiment, the reference-based transcriptome assembly was performed. We identified 418 EST-SSRs and 232 EST-SSR were selected, with trinucleotide repeats being the most frequent motif (380-90.9%), followed by composited (4.5%), di- (3.6%), and hexanucleotides (3.6%). A total of 145 EST-SSR (62.5%) were validated on seventeen macaúba samples, and 100 were considered polymorphic with PIC values ranging from 0.25 to 0.77. 

Genetic diversity analysis performed with the 20 most informative EST-SSRs showed a distinct separation of the different macaúba samples, according to the geographical location. Additionally, 145 markers were transferred in six other palm species resulting in 99% transferability rates (144) in Acrocomia intumescens, 98% (143) in Acrocomia totai, 80.7% (117 EST-EST) in samples of African oil palm (Elaeis guineensis) and peach palm (Bactris gasipaes), 70% (102) in juçara palm (Euterpe edulis) and 71.7% (104) in hat palm (Sabal causiarum). 

Analysis of genetic distance established distinct groups by genera. These are exploratory data but will support ongoing research with macaúba palm.

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Page: Repositório Unicamp

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