Sequence Variation and Expression Analysis of Seed Dormancy- and Germination-Associated ABA- and GA-Related Genes in Rice Cultivars

Fei Liu,Gang Wu,Hangxiao Zhang,Jing Sun,Jun Yu,Lili Hao,Weiwei Wang,Xiaomeng Ge

doi:10.3389/fpls.2011.00017

Abstract

Abscisic acid (ABA) and Gibberellic acid (GA) play key roles in regulating seed dormancy and germination. First, when examining germination of different rice cultivars, we found that their germination timing and dormancy status are rather distinct, coupled with different GA/ABA ratio. Second, we studied genomic sequences of ABA and GA dormancy- and germination-associated genes in rice and discovered single nucleotide polymorphisms and insertions/deletions (Indels) in both coding and regulatory sequences. We aligned all these variations to the genome assemblies of 9311 and PA64s and demonstrated their relevance to seed dormancy both quantitatively and qualitatively based on gene expression data. Third, we surveyed and compared differentially expressed genes in dry seeds between 9311 and PA64s to show that these differentially expressed genes may play roles in seed dormancy and germination.

Highlights

Seed dormancy has been defined as a temporary failure of seed germination under conditions that favor germination (Bewley, 1997)
We demonstrate that seed dormancy state in rice may be influenced by both gene sequence variation as well as expression patterns of Abscisic acid (ABA) and Gibberellic acid (GA) metabolic genes
Germination test and ABA/GA concentration measurement of rice seeds from various cultivars We initiated our study by carrying out a germination experiment using seeds from various cultivars (9311, Pei-Ai 64s (PA64s), IR24, SHOEMED, AZUCENA, DOURADO AGULHA, MAKALIOKA34, and IR36) with diverse genetic backgrounds (Figure 1)

Summary

Introduction

Seed dormancy has been defined as a temporary failure of seed germination under conditions that favor germination (Bewley, 1997). The initiation of dormancy can either occur in the dry state (after-ripening) or be triggered by imbibition under defined conditions in mature seeds (Gubler et al, 2005). Strong dormancy prevents grain such as barley from being re-planted immediately after harvest, causing delayed or non-uniform germination. Both situations would result in poor crop establishment and grain performance. Seed dormancy and germination are regulated by most plant hormones. ABA plays important roles in many cellular processes including seed development, dormancy, germination, vegetative growth, and environmental stress responses. In addition to hormone c ontent, the transition from the dormant to the nondormant state of many seeds is characterized by a decrease in ABA sensitivity and an increase in GA sensitivity (Chiwocha et al, 2005)

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Results

Conclusion