The roles of amino acid transporters in plant immunity

Plants require large amounts of nitrogen (N) for their growth and development. Amino acids (AAs) act as the predominant transport forms of N within plants, involve deeply in the entire life cycle of plants. Amino acid transporters (AATs) mediate the long-distance transfer of AAs from the source to the sink in plants and function in amino acid homeostasis. AATs regulate the plant growth and development and the immunity system for stress resistance that are triggered by infected pathogens including fungi, bacteria, viruses, and nematodes. In recent years, the functions and regulatory mechanisms of AAs and AATs in plant immunoreactions and disease resistance have achieved some remarkable breakthroughs. We elaborated the roles and metabolism of AATs in plant immunity. Meanwhile, we summarized the molecular mechanisms of amino acid permeases (AAPs), lysine and histidine transporters (LHTs), cationic amino acid transporters (CATs), and multiple acids moving in and out the transporter family (UMAMITs) in plant defense to pathogen diseases. LHT1 functions in root uptake and source-to-sink allocation of amino acids in plants, and modulates both plant growth and defense immunity. Taking Arabidopsis and rice (Oryza sative) LHT1 as an example, we highlighted how LHT1 responding to the attack of biotrophic, hemi biotrophic, or necrotrophic pathogens, and the divergent roles of LHT1 in monocotyledon and dicotyledon in the plant defenses. In addition, we establish a working model underlying the interplay of plants and pathogens for the AATs mediated regulatory processes of plant immunity. The researches needed for trade-off among the yield, quality and defense in plants included: 1) Which amino acids are the key nutrients or signaling molecules for plant defense? 2) What is the transition of amino acid signaling in plant cells during pathogen infection? 3) How do plant AATs sense pathogens? 4) How do plant AATs control nutrient exchange between plants and pathogens? 5) How do plant AATs modulate plant immunity in salicylic acid- and/or jasmonic acid-dependent manners? 6) Is there a crosstalk between plant and microbe genes during pathogen infection? The approaches will provide solutions for breeding ideal cultivars of high yield, excellent quality, and resistance to pathogenic attack.