ZIP genes are involved in the retransfer of zinc ions during the senescence of zinc-deficient rice leaves

Abstract

Zinc (Zn) is essential for human health, but rice often lacks sufficient amounts. Leaf senescence is a vital developmental stage during which nutrients are redistributed to other organs. However, Zn retransfer during deficiency is often overlooked. In this hydroponic experiment, we studied the effect of Zn deficiency on rice seedlings, specifically focusing on the fourth leaf under control and deficient conditions. Growth phenotype analysis showed that the growth of rice nodal roots was inhibited under Zn deficiency, and the fourth leaf exhibited accelerated senescence and increased Zn ion transfer. We conducted transcriptome analysis on the fourth leaf at two time points. The fourth leaf at the second time point under control conditions was used as the control and compared to when Zn ion content markedly decreased under control and deficiency conditions. Analyzing differentially expressed genes showed that Zn deficiency regulates more ZIP family genes involved in Zn ion retransfer in the leaves. OsZIP3 upregulation under Zn-deficient conditions may not be induced by Zn deficiency, whereas OsZIP4 is only induced during Zn deficiency. Gene Ontology enrichment analysis showed that Zn-deficient leaves mobilized more biological pathways (BPs) during aging, and the enrichment function differed from that of normal aging leaves. The most apparent “zinc ion transport” BP was stronger than that of normal senescence, possibly due to Zn-deficient leaves mobilizing large amounts of BP related to lipid metabolism during senescence. These results provide a basis for further functional analyses of genes and the study of trace element transfer during rice leaf senescence.