Abstract
PARP proteins are highly conserved homologs among the eukaryotic poly (ADP-ribose) polymerases. After activation, ADP-ribose polymers are synthesized on a series of ribozymes that use NAD+ as a substrate. PARPs participate in the regulation of various important biological processes, such as plant growth, development, and stress response. In this study, we characterized the homologue of PARP1 in B. rapa using RNA interference (RNAi) to reveal the underlying mechanism responding to drought stress. Bioinformatics and expression pattern analyses demonstrated that two copy numbers of PARP1 genes (BrPARP1.A03 and BrPARP1.A05) in B. rapa following a whole-genome triplication (WGT) event were retained compared with Arabidopsis, but only BrPARP1.A03 was predominantly transcribed in plant roots. Silencing of BrPARP1 could markedly promote root growth and development, probably via regulating cell division, and the transgenic Brassica lines showed more tolerance under drought treatment, accompanied with substantial alterations including accumulated proline contents, significantly reduced malondialdehyde, and increased antioxidative enzyme activity. In addition, the findings showed that the expression of stress-responsive genes, as well as reactive oxygen species (ROS)-scavenging related genes, was largely reinforced in the transgenic lines under drought stress. In general, these results indicated that BrPARP1 likely responds to drought stress by regulating root growth and the expression of stress-related genes to cope with adverse conditions in B. rapa.
Highlights
IntroductionDrought is a common abiotic stress that affects plant growth and limits crop yield and quality [1]
Introduction published maps and institutional affilDrought is a common abiotic stress that affects plant growth and limits crop yield and quality [1]
We constructed the phylogenetic relationship, gene structure, and functional domain of the Poly (ADP-ribose) polymerase (PARP) protein in three typical diploid Brassicaceae species, namely, A. thaliana, B. rapa, and B. oleracea, and analyzed the copy number of the PARP genes retained in their genome (Figure 1A)
Summary
Drought is a common abiotic stress that affects plant growth and limits crop yield and quality [1]. Long-term exposure to water-deficient conditions will affect the physiological responses of plants, such as the activities of hormone-metabolizing enzymes, the accumulation of reactive oxygen species (ROS), the opening and closing of stomata, and other characteristics, showing the phenotype of growth retardation [2,3,4]. ROS accumulation could cause oxidative damage to DNA and directly extract hydrogen from deoxyribose, leading to DNA single-strand and double-strand breaks, resulting in genome instability and plant aging [5]. The accumulation of ROS in plants will enhance plasma membrane oxidation and protein degradation, causing oxidative damage and affecting plant growth [6]. The root system is the most sensitive organ of plants to deal with iations
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