The free amino acids (AAs) occurred in soils/environments may represent a N-source for plant growth and might also serve as cues to regulate the root architectural formation. However, the detailed phenomenon and biological mechanism(s) of AAs’ effect on root growth and development are not well described. Recently, growth test of Arabidopsis on 18 proteinogenic L-AAs allowed us to identify the sensitivity of the root system growth to several AAs including leucine. Using combined approaches, including root growth-phenotyping on segmented medium-plates, histochemical analysis, microscopic assay, monitoring of cytosolic Ca²⁺ and tissue auxin distribution, transgenic recovery study and transcription profiling, we detailedly characterized properties of root growth on Leu, and consequently uncovered some putative molecular components for the sensitivity of the plant growth to Leu. Furthermore, at molecular and physiological levels, we revealed that a previously-reported amino-acid transporter with a novel function at the primary root tip should be a crucial molecular determinant involved in the Leu-modified root system growth. This transporter has been for the first time verified to permeate both Leu and Ile with a high-affinity in planta in our study, and its transcription was regulated by external and internal Leu and Ile. Profiling of AAs in roots of the transporter mutant and its transgenic complementary plants points to that the functional expression of this transporter might be critical for maintaining a metabolic balance of Leu-to-Ile in the root apex and, in turn, modulating Leu-sensitive root growth. Some interest aspects of this transporter-involved root growth and development in response to Leu will be discussed in the conference.

Dr Lai-Hua Liu completed his Ph.D. study in 2002 at Tuebingen University, Germany; and thereafter He conducted a postdoc job from 2003 to 2005 in the Department of Plant Sciences at Cambridge University, UK. Since 2004.11, he has become a full professor at China Agricultural University, working actively on plant molecular physiology involved in the nutrient transport and effective use, root growth and nutrient sensing, as well as plant response to environmental stresses including nutrients and temperature. He has published more than 45 articles in distinguished international journals including Science, The Plant Cell, Plant Physiology, New Phytologist, Science Signalling, Plant Science, Frontiers in Plant, Plant Methods etc. and has been serving as an editor-in-chef and editorial board member of some journals.