Abstract
Plants need abundant nitrogen and phosphorus for higher yield. Improving plant genetics for higher nitrogen and phosphorus use efficiency would save potentially billions of dollars annually on fertilizers and reduce global environmental pollution. This will require knowledge of molecular regulators for maintaining homeostasis of these nutrients in plants. Previously, we reported that the NITROGEN LIMITATION ADAPTATION (NLA) gene is involved in adaptive responses to low-nitrogen conditions in Arabidopsis, where nla mutant plants display abrupt early senescence. To understand the molecular mechanisms underlying NLA function, two suppressors of the nla mutation were isolated that recover the nla mutant phenotype to wild type. Map-based cloning identified these suppressors as the phosphate (Pi) transport-related genes PHF1 and PHT1.1. In addition, NLA expression is shown to be regulated by the low-Pi induced microRNA miR827. Pi analysis revealed that the early senescence in nla mutant plants was due to Pi toxicity. These plants accumulated over five times the normal Pi content in shoots specifically under low nitrate and high Pi but not under high nitrate conditions. Also the Pi overaccumulator pho2 mutant shows Pi toxicity in a nitrate-dependent manner similar to the nla mutant. Further, the nitrate and Pi levels are shown to have an antagonistic crosstalk as displayed by their differential effects on flowering time. The results demonstrate that NLA and miR827 have pivotal roles in regulating Pi homeostasis in plants in a nitrate-dependent fashion.
Highlights
High yielding crops require the application of large amounts of nitrogen (N) and phosphorus (P) fertilizers
In an attempt to isolate the regulatory genes for nitrogen and phosphorus homeostasis in plants, we identified the NITROGEN LIMITATION ADAPTATION (NLA) gene as having a role in plant adaptation under low-nitrogen conditions
The nla mutant was identified based on its altered growth response to N limitation. nla mutant plants failed to show several adaptive responses to low-N conditions, such as the inability to accumulate anthocyanin and abrupt early senescence compared to wild type (WT) plants [21]
Summary
High yielding crops require the application of large amounts of nitrogen (N) and phosphorus (P) fertilizers. Most of the crop plants are able to take up less than 40% of the applied N and P fertilizers and the rest of it is lost to the environment. This leads to an increase in crop production cost and significant global environmental damage by eutrophication of marine and fresh water ecosystems and gaseous loss to the atmosphere [1,2,3]. Developing crop varieties with higher nutrient use efficiency to restrict the excessive use of N and P fertilizer is required. A comprehensive knowledge of molecular mechanisms regulating N and P homeostasis in plants is a prerequisite
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