AUTHOR=An Baoguang , Lan Jie , Deng Xiaolong , Chen Silan , Ouyang Chao , Shi Huiyun , Yang Jing , Li Yangsheng 

TITLE=Silencing of D-Lactate Dehydrogenase Impedes Glyoxalase System and Leads to Methylglyoxal Accumulation and Growth Inhibition in Rice

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.02071

DOI=10.3389/fpls.2017.02071

ISSN=1664-462X

ABSTRACT=<p><sc>D</sc>-Lactate is oxidized by two classes of <sc>D</sc>-lactate dehydrogenase (<sc>D</sc>-LDH), namely, NAD-dependent and NAD-independent <sc>D</sc>-LDHs. Little is known about the characteristics and biological functions of <sc>D</sc>-LDHs in rice. In this study, a functional NAD-independent <sc>D</sc>-LDH (LOC_Os07g06890) was identified in rice, as a result of alternative splicing events. Characterization of the expression profile, subcellular localization, and enzymatic properties of the functional Os<sc>D</sc>-LDH revealed that it is a mitochondrial cytochrome-<italic>c</italic>-dependent <sc>D</sc>-LDH with high affinity and catalytic efficiency. Functional analysis of <italic>Os<sc>D</sc>-LDH</italic> RNAi transgenic rice demonstrated that Os<sc>D</sc>-LDH participates in methylglyoxal metabolism by affecting the activity of the glyoxalase system and aldo-keto reductases. Under methylglyoxal treatment, silencing of Os<sc>D</sc>-LDH in rice resulted in the accumulation of methylglyoxal and <sc>D</sc>-lactate, the decrease of reduced glutathione in leaves, and ultimately severe growth inhibition. Moreover, the detached leaves of <italic>Os<sc>D</sc>-LDH</italic> RNAi plants were more sensitive to salt stress. However, the silencing of Os<sc>D</sc>-LDH did not affect the growth under photorespiration conditions. Our results provide new insights into the role of NAD-independent <sc>D</sc>-LDHs in rice.</p>