TFT6 and TFT7, two different members of tomato 14-3-3 gene family, play distinct roles in plant adaption to low phosphorus stress

ABSTRACT

14-3-3 proteins are a large family of proteins but exact roles of their members in plant response to abiotic stresses are not clear, especially under nutrient deficiency. We investigated the expressions of all the tomato 14-3-3 gene family members (TFT1–TFT12) under low phosphorus stress (LP) and found that TFT6 belongs to the later responsive gene while TFT7 belongs to the early responsive gene. When the two genes were separately introduced into Arabidopsis and overexpressed, their plant growth under LP was much enhanced compared with wild-type plant. TFT6 overexpressing plants showed reduced starch synthase activity, reduced starch content but enhanced sucrose loading into phloem in the shoot under LP. TFT7 overexpressing plants had much enhanced H⁺ flux along their root tip and activity of plasma membrane H⁺-ATPase in the roots under LP. Our results suggest that TFT6 and TFT7 play different roles in plant adaption to LP. TFT6 acts mainly in leaves and is involved in the systemic response to LP by regulating leaf carbon allocation and increasing phloem sucrose transport to promote root growth, while TFT7 directly functions in root by activating root plasma membrane H⁺-ATPase to release more protons under LP.