Rice PCR1 Influences Grain Weight and Zn Accumulation in Grains

Proteins containing a placenta-specific 8 domain (PLAC8) function as major organ size regulators in Solanum lycopersicum and Zea mays, and putative metal ion transporters in Arabidopsis thaliana, Oryza sativa and Brassica juncea. However, it remains to be determined how PLAC8 domain-containing proteins fulfill such diverse roles. Here, we found that plant cadmium resistance 1 (PCR1) influences both the zinc (Zn) accumulation and weight of rice grains. OsPCR1-knockout and -knockdown lines produced lighter grains than the wild type, while OsPCR1-overexpression lines produced heavier grains. Furthermore, the grains of OsPCR1-knockdown lines contained substantially more Zn and less cadmium (Cd) concentration than the control, as did yeast heterologously expressing OsPCR1. Through sequence analysis of many different rice lines, we showed that the amino acid sequence of japonica-type PCR1 was distinct from that of indica-type and wild rice accessions. This difference was correlated with distinct Zn-related phenotypes. Japonica-type PCR1 had a shorter N-terminus than the other rice types, and yeast heterologously expressing japonica-type PCR1 was more sensitive to Zn than was yeast expressing indica-type PCR1. Furthermore, japonica-type grains accumulated less Zn than did indica-type grains. Our study suggests that rice PCR1 has important functions in maintaining metal ion homeostasis and grain weight and might have been selected for during domestication.

This work was supported by the Next-Generation Biogreen 21 Program for Agriculture & Technology Development (Project No. PJ01104801), Rural Development Administration, Republic of Korea

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