Transcript Profile in Vegetable Soybean Roots Reveals Potential Gene Patterns Regulating K Uptake Efficiency

Changkai Liu,Yansheng Li,Qiuying Zhang,Xiaobing Liu,Bingjie Tu,Xue Wang

doi:10.3390/agronomy10111796

Abstract

Significant differences have been reported in root K+ uptake between high potassium efficiency (HKE) and low potassium efficiency (LKE) in vegetable soybean genotypes. The ideal morphological and physiological characteristics of HKE have been defined. However, the mechanism by which HKE vegetable soybean genotypes efficiently uptake K remains unclear. By using representative materials, this study investigated the responses of root development to low K (LK) stress, and identified and assessed the key genes affecting high-efficiency K uptake between HKE and LKE vegetable soybean roots. The root growth of LKE was significantly inhibited under the LK condition. Compared with LKE, HKE had more lateral roots in both LK and CK (control) conditions. Lateral root of HKE was more preferentially responsive to exogenous IAA, with a wider response threshold to IAA concentration (from 0.1 to 1 µM). Transcriptome analysis revealed that LK induced transport-related genes up-regulated in HKE compared with LKE. In HKE, homologous genes of a K channel encoding gene potassium channel AKT1 (AKT1) and a K transporter gene high-affinity K+ transporter 5 (HAK5) were both highly expressed under the LK stress. Additionally, genes related to plant hormones signal transductions were also identified differentially expressed between the two genotypes. Plant hormone signaling involved in root morphological regulation pathways may play significant roles in improving the efficiency of vegetable soybean K+ uptake. A diagram showing possible molecular mechanisms in regulating root high-efficiency uptake K+ in vegetable soybean is proposed.

Highlights

Potassium (K) is one of the most important mineral nutrients, and is essential for crop yield and quality [1]
Root Morphology and High Potassium Efficiency in Vegetable Soybean associated with the ability to convert per unit potassium into more dry matter or yield [33], which has been found in previous studies [5,6], and confirmed in this study
The auxin signal associated with other hormone signals would be an important mechanism affecting lateral root formation of HKE genotype

Summary

Introduction

Potassium (K) is one of the most important mineral nutrients, and is essential for crop yield and quality [1]. Cultivars with high efficiency of uptake and use of K nutrient are widely used to reduce the use of chemicals in agriculture [2], and are an effective way of reducing K fertilizer cost [3]. Vegetable soybean (Glycine max (L.) Merrill) is a crop with a high K demand [4]. Based on the selection of highly efficient K uptake and use associated with specific morphological and physiological characteristics, representative high K efficiency vegetable soybean genotypes have been identified that have efficient dry matter and K redistribution ability and high specific root uptake K ability [5,6]. Understanding the potassium uptake mechanism is of great significance for the development of K-efficient and low K+ tolerant cultivars, and has attracted extensive attention [7]

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