Microarray analysis of juvenile and mature cuttings of Eucalyptus grandis revealed developmental regulation of nitrate reductase which potentially influences nitric oxide production and adventitious root formation

ABSTRACT: 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.

ORGANISM(S): Eucalyptus grandis

SUBMITTER: Ron Ophir 

PROVIDER: E-GEOD-36317 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress