Oral Presentation International Plant Molecular Biology Conference 2024

AMF transporters are important for cellular ammonium management and nitrogen delivery to developing seeds (#378)

Wenjing Li 1 2 , Apriadi Situmorang 3 , Kamal Uddin 1 , Danielle Maurkiewicz 3 , Bei Zhang 2 , Tongtong Liu 2 , Guangda Ding 2 , Megan Shelden 3 , Stephen Tyerman 3 , Chuang Wang 2 , Brent N Kaiser 1
  1. Sydney Institute of Agriculture, The University of Sydney, Sydney, NSW, Australia
  2. Key Laboratory of Arable Land Conservation, Huazhong Agricultural University, Wuhan, China
  3. Agriculture Food and Wine, The University of Adelaide, Urrbrae, SA, Australia

The ammonium facilitator (AMF) transport proteins are related to DHA2 Drug:H+ antiporters, linked to multidrug resistance and H+-dependent antiport of amino acids, cations, siderophores and glutathione in yeast1. We have characterized the functional activities of three AMF genes in Arabidopsis and the single AMF homolog in Rice for their role in NH4+ transport, cellular NH4+ homeostasis, growth and nitrogen redistribution. AMF proteins are exclusively found at the endoplasmic reticulum (AtAMF1;1), the tonoplast (AtAMF1;2) and the plasma membrane (ATAMF1;3, OsAMF1). Using yeast cell lines with variable NH4+ sensitivities (31019b and CY162), AtAMF1;2 and AtAMF1;3 were found to transport and/or retain cellular NH4+ in 31019b cells. The tonoplast localized AtAMF1;2 increased yeast tolerance to toxic concentrations of NH4+ (>100 mM) when expressed in a plasma membrane K+ transport and NH4+ sensitive mutant (CY162). A disruption of AMF activity through T-DNA gene silencing, initiated an early senescence phenotype in Arabidopsis leaves (chlorosis) and a reduction in seed size, seed yield and seed nitrogen accumulation. A similar trait of leaf senescence and necrosis, reduced seed size and compromised seed nitrogen was observed in Osamf1 mutants. AMF overexpression (Arabidopsis or Rice) could recover the loss AMF activity in AMF KO plants. The distinct cellular membrane localisation of the AMF protein family suggests a role in the intercellular management of NH4+ that when disrupted increases NH4+ sensitivities in plants and disrupts the recycling and redistribution of shoot N to developing reproductive tissues.