Abstract
BackgroundThe root architecture of grafted apple (Malus spp.) is affected by various characteristics of the scions. To provide information on the molecular mechanisms underlying this influence, we examined root transcriptomes of M. robusta rootstock grafted with scions of wild-type (WT) apple (M. spectabilis) and a more-branching (MB) mutant at the branching stage.ResultsThe growth rate of rootstock grafted MB was repressed significantly, especially the primary root length and diameter, and root weight. Biological function categories of differentially expressed genes were significantly enriched in processes associated with hormone signal transduction and intracellular activity, with processes related to the cell cycle especially down-regulated. Roots of rootstock grafted with MB scions displayed elevated auxin and cytokinin contents and reduced expression of MrPIN1, MrARF, MrAHP, most MrCRE1 genes, and cell growth-related genes MrGH3, MrSAUR and MrTCH4. Although auxin accumulation and transcription of MrPIN3, MrALF1 and MrALF4 tended to induce lateral root formation in MB-grafted rootstock, the number of lateral roots was not significantly changed. Sucrose, fructose and glucose contents were not decreased in MB-grafted roots compared with those bearing WT scions, but glycolysis and tricarboxylic acid cycle metabolic activities were repressed. Root resistance and nitrogen metabolism were reduced in MB-grafted roots as well.ConclusionsOur findings suggest that root growth and development of rootstock are mainly influenced by sugar metabolism and auxin and cytokinin signaling pathways. This study provides a basis that the characteristics of scions are related to root growth and development, resistance and activity of rootstocks.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2484-x) contains supplementary material, which is available to authorized users.
Highlights
The root architecture of grafted apple (Malus spp.) is affected by various characteristics of the scions
To assess the relative proportion of lateral root (LR) growth to total root growth, we used the ratio of LR number to total root weight
This ratio was higher in MB-bearing rootstock. This ratio progressively decreased in both MB- and WT-bearing rootstocks as the growth period was extended. These results indicate that root growth, the primary root, is the main process
Summary
The root architecture of grafted apple (Malus spp.) is affected by various characteristics of the scions. To provide information on the molecular mechanisms underlying this influence, we examined root transcriptomes of M. robusta rootstock grafted with scions of wild-type (WT) apple (M. spectabilis) and a more-branching (MB) mutant at the branching stage. Apple pro- Grafting experiments have revealed that plant vascular duction relies heavily on grafting, a technique that com- systems function as transportation corridors for horbines well-adapted rootstocks with high-quality scions. Li et al BMC Genomics (2016) 17:150 has demonstrated that grafted gain-of-function transcripts can impact tissue development, thereby influencing features such as leaf shape and root architecture [1, 2, 9,10,11]. The main targets of sugar signals are auxin, ABA and CK signalling processes [20, 21]
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