Uncovering the role of apocarotenoids in the arbuscular mycorrhiza symbiosis via mutation and knockdown of biosynthetic genes
Final Report Abstract
The main focus of the work for elucidating the function of C 13/C14 apocarotenoids in the arbuscular mycorrhizal symbiosis was put on the mtpt4-1 mutant, which exhibits an increase in degenerated and dead arbuscules correlated with the loss-of-function of the single AM-specific phosphate transporter MtPT4. However, it turned out that the premature-death arbuscule phenotype described thus far mainly from single infection units using the specific fungus Glomus versiforme, was not as clearcut as we expected in our experimental system. Moreover, there was always a very high variation in colonization and arbuscule morphologies. It can be speculated that each arbuscule is regulated more or less individually by the root demand for nutrients, mainly phosphate, and by its performance in delivering phosphate or other nutrients to the plant. Therefore, we failed to show differences in C13/C14 metabolite accumulation and transcript levels in root extracts, since there is no synchronous regulation of arbuscule development and degradation. We could show by the immunolocalization experiments using the DXR antibody that similar isoprenoid biosynthetic activities presumably related to local C13/C14 apocarotenoid biosynthesis occur in both the WT and the mtpt4-1 mutant. This implies that arbuscule degradation mechanisms are similar in the two genotypes and that indeed transporter-mediated phosphate delivery to the root cell through the periarbuscular membrane is a determinant of the arbuscular life cycle. However, we are still quite far from understanding the functioning of the AM symbiosis in the late symbiotic phase, which is much less studied than early recognition phases. The role of the C13/C14 apocarotenoids in the symbiotic stage of the symbiosis beyond the current model still awaits further clarification.
Publications
- (2010) Apocarotenoids: hormones, mycorrhizal metabolites and aroma volatiles. Planta 232: 1-17
Walter MH, Floss DS, Strack D
- (2010) SlCCD7 controls strigolactone biosynthesis, shoot branching and mycorrhizainduced apocarotenoid formation in tomato. Plant Journal 61: 300-311
Vogel JT, Walter MH, Giavalisco P, Lytovchenko A, Kohlen W, Charnikhova T, Simkin AJ, Goulet C, Strack D, Bouwmeester HJ, Fernie AR, Klee HJ
- (2010) The isogene 1-deoxy-D-xylulose 5-phosphate synthase 2 controls isoprenoid profiles, precursor pathway allocation, and density of tomato trichomes. Molecular Plant 3: 904-916
Paetzold H, Garms S, Bartram S, Wieczorek J, Uros-Gracia EM, Rodriguez- Concepcion M, Boland W, Strack D, Hause B, Walter MH
- (2011) Carotenoids and their cleavage products: Biosynthesis and functions. Natural Product Reports 28: 663-692
Walter MH, Strack D
- (2013) Control of plastidial precursor supply:divergent 1-deoxy-d-xylulose 5-phosphate synthase (DXS) isogenes regulate the allocation to primary or secondary metabolism. In TJ Bach, M Rohmer, eds, Isoprenoid synthesis in plants and microorganisms. Springer, New York, pp 251-270
Walter MH, Floss, DS, Paetzold H, Manke K, Vollrath J, Brandt W, Strack D
- (2013) Role of carotenoid metabolism in the arbuscular mycorrhizal symbiosis. In F de Bruijn, ed, Molecular Microbial Ecology of the Rhizosphere, Vol 1. Wiley-Blackwell, pp 513-524
Walter MH
- (2015) Differential spatio-temporal expression of carotenoid cleavage dioxygenases regulates apocarotenoid fluxes during AM symbiosis. Plant Science 230: 59-69
Lopez-Raez JA, Fernandez I, Garcia JM, Berrio E, Bonfante P, Walter MH, Pozo MJ
(See online at https://doi.org/10.1016/j.plantsci.2014.10.010) - (2015) Evolution of root-specific carotenoid precursor pathways for apocarotenoid signal biogenesis. Plant Science, Volume 233, April 2015, Pages 1-10
Walter MH, Stauder R, Tissier A
(See online at https://doi.org/10.1016/j.plantsci.2014.12.017)
