On June 6, 2025, the research group led by Academician Xiaofeng Cao from the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences published a study in Proceedings of the National Academy of Sciences of the United States of America (PNAS), titled:
“Control of seed-to-seedling transition by an upstream open reading frame in ABSCISIC ACID DEFICIENT 2”.
This work systematically dissects the dynamic regulatory networks at both the transcriptional and translational levels that govern the seed-to-seedling transition.
In the course of this research, JIUPO plant growth chambers were employed to precisely simulate specific environmental conditions for Arabidopsis and rice germination assays, allowing for accurate quantification of germination rates.
Pre-harvest sprouting (PHS) is a phenomenon caused by insufficient seed dormancy, in which grains begin to germinate on the spike under prolonged wet conditions before harvest, resulting in significant yield losses in major cereal crops worldwide. Understanding the molecular mechanisms underlying seed dormancy and germination is therefore of strategic importance for enhancing crop stress resilience and ensuring global food security.
Recent research has demonstrated that translation of stored mRNAs is essential for early seed germination. Various cis-regulatory elements within mRNA sequences play crucial roles in regulating translation, yet their specific functions during seed germination remain largely unexplored.
Figure 1: Delayed germination in ribosomal mutants is partially dependent on ABA levels
This study employed transcriptome and translatome profiling to comprehensively elucidate the dynamic regulatory networks during germination. Using ribosomal-deficient mutants as a model, the researchers demonstrated that the delayed germination phenotype is associated with ABA2, a key gene in abscisic acid (ABA) biosynthesis. Notably, an upstream open reading frame (uORF) in the 5′ untranslated region (UTR) of ABA2 was found to repress translation of its downstream coding sequence (CDS).
Further investigation revealed that this regulatory mechanism is highly conserved in rice. By using CRISPR-Cas9 gene editing to specifically disrupt the uORF of OsABA2, the researchers effectively suppressed pre-harvest sprouting. Moreover, two major haplotypes of this uORF were identified across rice varieties, which modulate OsABA2 expression levels and thereby affect PHS resistance.
This work uncovers a critical role for translational regulation and natural genetic variation in seed dormancy and germination, and offers novel strategies for crop genetic improvement.
Figure 2. Working model of the ABA2 uORF-mediated translational regulation
Dr. Zhen Wang (Associate Researcher) and Xiaofan Zhang (PhD candidate) are co–first authors of the paper.
Prof. Xiaofeng Cao and Dr. Zhen Wang are corresponding authors.
This research was supported by the Key Projects of the Ministry of Agriculture and Rural Affairs of China, the National Natural Science Foundation of China, and other funding programs.