| 1. |
- Eklund, D. Magnus, et al.
(författare)
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Homologues of the Arabidopsis thaliana SHI/STY/LRP1 genes control auxin biosynthesis and affect growth and development in the moss Physcomitrella patens
- 2010
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Ingår i: Development. - : The Company of Biologists. - 0950-1991 .- 1477-9129. ; 137:8, s. 1275-1284
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Tidskriftsartikel (refereegranskat)abstract
- The plant hormone auxin plays fundamental roles in vascular plants. Although exogenous auxin also stimulates developmental transitions and growth in non-vascular plants, the effects of manipulating endogenous auxin levels have thus far not been reported. Here, we have altered the levels and sites of auxin production and accumulation in the moss Physcomitrella patens by changing the expression level of homologues of the Arabidopsis SHI/STY family proteins, which are positive regulators of auxin biosynthesis genes. Constitutive expression of PpSHI1 resulted in elevated auxin levels, increased and ectopic expression of the auxin response reporter GmGH3pro:GUS, and in an increased caulonema/chloronema ratio, an effect also induced by exogenous auxin application. In addition, we observed premature ageing and necrosis in cells ectopically expressing PpSHI1. Knockout of either of the two PpSHI genes resulted in reduced auxin levels and auxin biosynthesis rates in leafy shoots, reduced internode elongation, delayed ageing, a decreased caulonema/chloronema ratio and an increased number of axillary hairs, which constitute potential auxin biosynthesis sites. Some of the identified auxin functions appear to be analogous in vascular and non-vascular plants. Furthermore, the spatiotemporal expression of the PpSHI genes and GmGH3pro:GUS strongly overlap, suggesting that local auxin biosynthesis is important for the regulation of auxin peak formation in non-vascular plants.
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| 2. |
- Ohlsson, Anna B., et al.
(författare)
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Cell suspension cultures of Populus tremula x P. tremuloides exhibit a high level of cellulose synthase gene expression that coincides with increased in vitro cellulose synthase activity.
- 2006
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Ingår i: Protoplasma. - : Springer Science and Business Media LLC. - 0033-183X .- 1615-6102. ; 228:4, s. 221-9
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Tidskriftsartikel (refereegranskat)abstract
- Compared to wood, cell suspension cultures provide convenient model systems to study many different cellular processes in plants. Here we have established cell suspension cultures of Populus tremula L. x P. tremuloides Michx. and characterized them by determining the enzymatic activities and/or mRNA expression levels of selected cell wall-specific proteins at the different stages of growth. While enzymes and proteins typically associated with primary cell wall synthesis and expansion were detected in the exponential growth phase of the cultures, the late stationary phase showed high expression of the secondary-cell-wall-associated cellulose synthase genes. Interestingly, detergent extracts of membranes from aging cell suspension cultures exhibited high levels of in vitro cellulose synthesis. The estimated ratio of cellulose to callose was as high as 50 : 50, as opposed to the ratio of 30 : 70 so far achieved with membrane preparations extracted from other systems. The increased cellulose synthase activity was also evidenced by higher levels of Calcofluor white binding in the cell material from the stationary-phase cultures. The ease of handling cell suspension cultures and the improved capacity for in vitro cellulose synthesis suggest that these cultures offer a new basis for studying the mechanism of cellulose biosynthesis.
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