Red soils in southern China are the typical soil type of tropical and subtropical regions. Formed under hot and humid climates, these soils exhibit low pH and are rich in iron oxides — properties that generally hinder crop growth. Although most rice cultivars can grow normally in iron-rich red soils, the genetic basis of this adaptability has remained unclear.

 

Recently, a collaborative study between the team of Dr. Lei Li (Peking University Institute of Advanced Agricultural Sciences / Shandong Laboratory of Advanced Agriculture Sciences in Weifang / State Key Laboratory of Wheat Improvement) and the team of Dr. Chunming Liu (Institute of Botany, Chinese Academy of Sciences) was published in New Phytologist. Their paper, titled “OsSPL9 promotes Cu uptake and translocation in rice grown in high-Fe red soil,” reveals the genetic mechanism by which the copper-homeostasis transcription factor OsSPL9 mediates rice adaptation to high-iron red soils.

 

Figure 1. The rice mutant rss1 is stunted when grown in high-iron red soil.

 

Using forward genetic screening, the authors identified a red-soil-sensitive rice mutant, rss1. In Hainan’s high-iron red soil, rss1 exhibited severe growth inhibition. This phenotype was milder in Sichuan red soil with lower iron levels and absent in Beijing brown soil (Figure 1). Physiological assays showed that, under red-soil/high-iron conditions, rss1 plants accumulated more iron but less copper in both roots and shoots; copper supplementation fully reversed the growth defect. Map-based cloning revealed that RSS1 encodes the rice copper-homeostasis transcription factor OsSPL9, which is expressed in the pericycle cells and the xylem parenchyma cells surrounding vessels. Under high-iron stress, OsSPL9 binds to the promoters of copper-transporter genes such as OsYSL16, OsCOPT1 and OsCOPT5, activating their expression. Over-expression of OsYSL16 partially rescued the rss1 phenotype. Thus, OsSPL9 enables rice to adapt to red-soil environments by activating copper-transporter gene expression, thereby alleviating copper deficiency caused by high iron (Figure 2).

 

Figure 2. OsSPL9 activates copper-transporter genes to overcome copper deficiency under high-iron stress

 

This study clarifies the coordinated regulation of iron and copper nutrition in plants and provides a theoretical basis for breeding crop varieties adapted to high-iron red soils, which is of great significance for improving productivity on marginal lands. Dr. Lei Li and Dr. Chunming Liu are the corresponding authors of the paper

 

Original article: https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.70074