Does the upstream region possessing MULE-like sequence in rice upregulate PsbS1 gene expression?

Mohammed Nuruzzaman,Rika Amada,Ichiro Kasajima,Tatsuo Kanno,Maki Kawai-Yamada,Yoshiki Habu,Toshiki Ishikawa,Hirofumi Uchimiya

doi:10.1371/journal.pone.0102742

Abstract

The genomic nucleotide sequences of japonica rice (Sasanishiki and Nipponbare) contained about 2.7-kb unique region at the point of 0.4-kb upstream of the OsPsbS1 gene. In this study, we found that japonica rice with a few exceptions possessing such DNA sequences [denoted to OsMULE-japonica specific sequence (JSS)] is distinct by the presence of Mutator-like-element (MULE). Such sequence was absent in most of indica cultivars and Oryza glaberrima. In OsMULE-JSS1, we noted the presence of possible target site duplication (TSD; CTTTTCCAG) and about 80-bp terminal inverted repeat (TIR) near TSD. We also found the enhancement ofOsPsbS1 mRNA accumulation by intensified light, which was not associated with the DNA methylation status in OsMULE/JSS. In addition, O. rufipogon, possible ancestor of modern rice cultivars was found to compose PsbS gene of either japonica (minor) or indica (major) type. Transient gene expression assay showed that the japonica type promoter elevated a reporter gene activity than indica type.

Highlights

Non-photochemical quenching (NPQ) regulates energy conversion in photosystem II, thereby protecting plants from photoinhibition
Regarding a typical Mutator-like elements (MULEs) characteristics, we found the presence of 80-bp terminal inverted sequences on the opposite ends of Oryza sativa (Os) OsMULE/japonica specific sequence (JSS) in japonica rice, cv
The Mu and MULEs were distinguishable from other DNA transposable elements by having a 9 to 11-bp target site duplication (TSD) that most likely formed during transposition into a new genome location

Summary

Introduction

Non-photochemical quenching (NPQ) regulates energy conversion in photosystem II, thereby protecting plants from photoinhibition. Plants dissipate unused light energy in the antenna proteins of PSII. This mechanism is called energy-dependent thermal dissipation, which can be measured as a component of NPQ. Photoinhibition induced by high illumination results in photo damage with inactivation of PSII. We observed the NPQ capacity in a number of rice cultivars; NPQ was triggered by high light intensities [1]. Photoinhibition is caused by high light stress: excessive energy results in photodamage with inactivation of the PSII machinery. A decrease in the photochemical rate constant and thermal loss of energy is triggered by photoinhibition through inactivation of a part of the PSII reaction center. With a few exceptions, there was no difference in terms of NPQs between subgroups within indica (aus and indica) or within some japonica subgroups (temperate japonica and tropical japonica) [1]

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