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Abscisic acid signalling mediates biomass trade‐off and allocation in poplar

Yu, Dade, Wildhagen, Henning, Tylewicz, Szymon, Miskolczi, Pal C., Bhalerao, Rishikesh P., Polle, Andrea
Thenew phytologist 2019 v.223 no.3 pp. 1192-1203
Populus tremula, RNA interference, abscisic acid, acclimation, biomass production, climate, drought, drought tolerance, dry matter partitioning, genes, genetic engineering, genetically modified organisms, irrigated conditions, leaf area, leaves, roots, second growth, stomatal conductance, tree height, trees, winter
Abscisic acid (ABA) is a well known stress hormone regulating drought adaptation of plants. Here, we hypothesised that genetic engineering of genes involved in ABA stress signalling and photoperiodic regulation affected drought resistance by trade‐off with biomass production in perennial poplar trees. We grew Populus tremula × tremuloides wild‐type (T89) and various transgenic lines (two transformation events of 35S::abi1‐1, 35S::RCAR, RCAR:RNAi, 35S::ABI3, 35S::AREB3, 35S::FDL1, FDL1:RNAi, 35S::FDL2 and FDL2:RNAi) outdoors and exposed them to drought in the second growth period. After the winter, the surviving lines showed a huge variation in stomatal conductance, leaf size, whole‐plant leaf area, tree height, stem diameter, and biomass. Whole‐plant leaf area was a strong predictor for woody biomass production. The 35S::AREB3 lines were compromised in biomass production under well irrigated conditions compared with wild‐type poplars but were resilient to drought. ABA signalling regulated FDL1 and FDL2 expression under stress. Poplar lines overexpressing FDL1 or FDL2 were drought‐sensitive; they shed leaves and lost root biomass, whereas the FDL RNAi lines showed higher biomass allocation to roots under drought. These results assign a new function in drought acclimation to FDL genes aside from photoperiodic regulation. Our results imply a critical role for ABA‐mediated processes in balancing biomass production and climate adaptation.