Molecular Mechanisms Regulating Carbohydrate Metabolism During Lolium perenne Regrowth Vary in Response to Nitrogen and
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Molecular Mechanisms Regulating Carbohydrate Metabolism During Lolium perenne Regrowth Vary in Response to Nitrogen and Gibberellin Supply Qianhe Liu1 · Susanne Rasmussen1,3 · Linda J. Johnson1 · Hong Xue1 · Anthony J. Parsons3 · Chris S. Jones1,2 Received: 14 May 2019 / Accepted: 14 January 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The promoting effects of both high nitrogen (N) and exogenous gibberellin (GA) supply on regrowth of Lolium perenne have been widely reported. The mobilisation of carbohydrate reserves in response to N is a critical mechanism for promoting plant regrowth. However, our knowledge about GA regulation of carbohydrate metabolism remains limited. Here, we analysed the effects of both N and exogenous GA on the molecular mechanisms controlling perennial ryegrass regrowth and investigated the similarities and differences. Our analyses show that both high N and exogenous GA supply lead to a decline in the accumulation of carbohydrate reserves, but the regulatory mechanisms responsible for this decline varied between N and GA supply. The effects of elevated N were mainly through declining fructan biosynthesis which results in improving photosynthate use efficiency to promote plant regrowth, whereas the application of exogenous GA resulted in an increase in the hydrolytic activities of fructan exohydrolase and invertases capable of cleaving reserved carbohydrates to release energy sources for plant regrowth. Keywords Perennial ryegrass · Regrowth · Fructans · Exogenous gibberellin · Nitrogen · Gene expression
Introduction Intense pasture-based animal production systems are strongly dependent on nitrogen (N) supply and face mounting pressure to mitigate resource-driven adverse environment impacts, such as nitrous oxide ( N2O) emissions and nitrate (NO3−) leaching. In New Zealand the primary source of N2O emissions, 57% of the total anthropogenic N 2O emissions (Ministry for the Environment 2013), comes directly from soils following N fertilisation and excreta deposition Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00344-020-10070-y) contains supplementary material, which is available to authorised users. * Chris S. Jones [email protected] 1
Grasslands Institute, AgResearch Ltd., Palmerston North, New Zealand
2
Present Address: International Livestock Research Institute (ILRI), Nairobi, Kenya
3
Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand
by grazing ruminants. One root cause of this high N2O emission is the high rate of N supply to the ruminant as part of a pasture-based diet. This leads to an excessive N intake per animal that is voided, predominantly in urine, adding to the concentrations of highly labile mineral N in soils already supplied with mineral N fertiliser (Parsons et al. 2013). A decrease in N fertilisation of soil and concurrent increase in carbohydrate content of forages, the latter providing a readily fermentable source
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