Rice RBH1 Encoding A Pectate Lyase is Critical for Apical Panicle Development.

Dong He,Tuan Long,Rui Liang,Ying Yang,Changyin Wu

doi:10.3390/plants10020271

Abstract

Panicle morphology is one of the main determinants of the rice yield. Panicle abortion, a typical panicle morphological defect results in yield reduction due to defective spikelet development. To further elucidate the molecular mechanism of panicle abortion in rice, a rice panicle bald head 1 (rbh1) mutant with transfer DNA (T-DNA) insertion showing severely aborted apical spikelets during panicle development was identified and characterized. The rbh1-1 mutant showed obviously altered cell morphology and structure in the degenerated spikelet. Molecular genetic studies revealed that RBH1 encodes a pectate lyase protein. Pectate lyase-specific activity of Rice panicle Bald Head 1 (RBH1) protein assay using polygalacturonic acid (PGA) as substrates illustrated that the enzyme retained a significant capacity to degrade PGA. In addition, immunohistochemical analysis showed that the degradation of pectin is inhibited in the rbh1-1 mutant. Further analysis revealed that a significant increase in reactive oxygen species (ROS) level was found in degenerated rbh1-1 spikelets. Taken together, our findings suggest that RBH1 is required for the formation of panicle and for preventing panicle abortion.

Highlights

In rice, the mechanisms of panicle development have been studied preliminary by research on a number of genes
Consistent with the observed panicle phenotype, the number of secondary branches (Figure 1F) and grains per panicle (Figure 1H) were significantly reduced in the mutant. These results suggest that Rice panicle Bald Head 1 (RBH1) is necessary for the panicle development
Earlier research has showed that some key genes such as LAX PANICLE1 (LAX1) and LAX PANICLE2 (LAX2) are mainly involved in the initiation/maintenance of rice axillary meristem

Summary

Introduction

The mechanisms of panicle development have been studied preliminary by research on a number of genes. All of the above genes are involved in the initiation of the branch meristem and the differentiation of the spikelet primordia, but the research focused on the regulation of branch elongation and floret formation is deficient. The loss of function of OsALMT7 results in a pleiotropic phenotype, including panicle apical abortion and short panicle length [10]. Physiological and biochemical experiments indicated that the loss of function of SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 6 (SPL6) gene could bring out the up-regulation of Inositol-Requiring Enzyme 1 (IRE1), eventually leading to cell death in the rice panicle. The disruption of Calcineurin B-Like ProteinInteracting Protein Kinase 31 (OsCIPK31) would result in the cell death during panicle development. The oscipk mutant displays reduced spikelet number per panicle and brown lesions on glumes [14]

Methods

Results

Conclusion