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Proteomic profiles during adventitious rooting of Eucalyptus species relevant to the cellulose industry (Formation)

ABSTRACT: Adventitious rooting (AR) is an obligatory step for vegetative propagation of commercial woody species. Paper industries have interest in Eucalyptus globulus Labill and its hybrids due to low lignin and lipid contents, which facilitate cellulose extraction. However, this species and some of its hybrids are recalcitrant to rooting, often requiring exogenous auxin supply. Here we performed a comparative analysis of proteome changes during AR of E. globulus and the easy-to-root species Eucalyptus grandis W. Hill and the effects of exogenous auxin in different phases of the process (induction and formation), using a label-free quantification method. We identified 398 differentially abundant proteins, which were predicted to be involved in different biological pathways, mainly oxidative stress, energy metabolism and photosynthesis. Notable differences between species included proteins involved in oxidative stress, carbon and secondary metabolism. Exogenous auxin appeared to affect the availability of carbon sources and other phytohormones, besides cell cycle and microtubule- related proteins. Important players were also identified in each phase of AR. This is the first in depth analysis of protein changes during AR in Eucalyptus. The findings can be used in future studies to evaluate rooting competence in different genotypes and provide leads for AR improvement.

INSTRUMENT(S): SYNAPT G2-Si

ORGANISM(S): Eucalyptus Grandis Eucalyptus Globulus (blue Gum)

TISSUE(S): Plant Cell, Whole Plant

SUBMITTER: Arthur Fett-Neto

LAB HEAD: Arthur G. Fett-Neto

PROVIDER: PXD013925 | Pride | 2019-08-19

REPOSITORIES: Pride

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Project description:Rooting capability is one of the economically traits lost during the juvenile to mature phase change in woody plants. A comprehensive microarray analysis was performed to compare the profiles of gene expression in juvenile and mature cuttings from E. grandis, either auxin treated or untreated on days, 0, 1, 3, 6, 9 and 12 post excision. At the end of the experiment, root primordia were observed only in auxin treated juvenile cuttings. Clustering the expression profiles revealed that the time after excision contributed to expression differences more than the age or auxin. Maximum differences contributed by the age and auxin occurred on day 6 which correlated with the kinetics of root primordia formation. These included genes related to the microtubules (MTs) system. Therefore, expression of 42 transcripts annotated as tubulin or MTs associated proteins (MAPs) was validated in the same RNA samples. The results suggest developmental and auxin regulation of MTs. To determine the relevance to adventitious root (AR) formation, subtle perturbations to MTs were performed with trifluralin during induction. While juvenile cuttings were not affected, improved rooting was obtained in mature cuttings. Taken together it suggests that specific MTs remodeling is required for AR formation in E. grandis. mRNA samlpes from mature and juvenile Eucalyptus sections immediately after cutting served as contorls. The rest of the samples were mature and juvenile sections, treated of not treated with Auxin, 1, 3, 6, 9 and 12 days after the prunning. At each time point, a loop design was performed consisting of a juvenile untreated vs. mature untreated array, a matrue untreated vs. mature auxin treated array, a matrue auxin treated vs. juvenile auxin treated array, and a juvenile auxin treated vs. juvenile untreated array. additional arrays connected between these loops, and between them and the time 0 controls. Most conditions had 3 replicates, but mature-untreated-day1 had 4 replicates, and three conditions had 2 replicates each: Juvenile-auxin-treated-day1, juvenile-untreated-day6, and mature-auxin-treated-day9.

Project description:The loss of rooting capability following the transition from the juvenile to the mature phase is a known phenomenon in woody plant development. Eucalyptus grandis was used here as a model system to study the differences in gene expression between juvenile and mature cuttings. RNA was prepared from the base of the two types of cuttings before root induction and hybridized to a DNA microarray of E. grandis. In juvenile cuttings, 363 transcripts were specifically upregulated, enriched in enzymes of oxidation/reduction processes. In contrast, in mature cuttings, 245 transcripts were specifically upregulated, enriched in transcription factors involved in the regulation of secondary metabolites. A gene encoding for nitrate reductase (NIA), an enzyme that is known to be involved in nitric oxide (NO) production, was among the genes that were upregulated in juvenile cuttings. Concomitantly, a transient burst of NO upon excision was higher in juvenile cuttings than in mature ones. Treatment with a NO donor improved rooting of both juvenile and mature cuttings. A single NIA gene was found in the newly released E. grandis genome sequence, the cDNA of which was isolated, overexpressed in Arabidopsis plants and shown to increase NO production. Therefore, higher levels of NIA in E. grandis juvenile cuttings might lead to their better ability to produce NO and form adventitious roots. The Arabidopsis transgenic plants did not exhibit significantly increased lateral or adventitious roots, suggesting that spatial and temporal rather than a constitutive increase in NO is favorable for root formation. E. grandis seedlings were grown from seeds to the age of 6-7 months. The seedlings were pruned either at 10-15 cm or at 150-200 cm above the ground. The newly developed shoots were used as cuttings. To induce rooting, auxin (6000 ppm of K-IBA), was applied by quick dipping (20 sec). Stem cuttings taken from low-pruned seedlings were found to be easy-to root, exhibiting 45% rooting after 14 days and 60% after 35 days. These cuttings were defined as juvenile (RNA from two biological replicates was extracted). In contrast, stem cuttings taken from high pruned seedlings, barely rooted (5%) after 35 days, and were defined as mature (RNA from two biological replicates was extracted). The two biological replicates was used to dye swap experimental design.

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Proteomic profiles during adventitious rooting of Eucalyptus species relevant to the cellulose industry (Formation)

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