Abstract
Aluminum (Al) toxicity is an important barrier to soybean (Glycine max (L.) Merr.) production in acid soils. However, little is known about the genes underlying Al tolerance in soybean. We aim to find the key candidate genes and investigate their roles in soybean tolerance to Al toxicity in this study. Comparative transcriptome analyses of the Al-tolerant (KF) and Al-sensitive (GF) soybean varieties under control and Al stress at 6, 12, and 24 h were investigated. A total of 1411 genes showed specific up-regulation in KF or more up-regulation in KF than in GF by Al stress, which were significantly enriched in the GO terms of peroxidase (POD) activity, transporter activity (including the known Al tolerance-related ABC transporter, ALMT, and MATE), and four families of transcription factors (AP2, C3H4, MYB, WRKY). The expression levels of seven POD genes were up-regulated by Al stress for at least one time point in KF. The H2O2 pretreatment significantly improved Al tolerance of KF, which is likely due to increased POD activity induced by H2O2. Our results suggest that PODs play important roles in soybean tolerance to Al toxicity. We also propose a list of candidate genes for Al tolerance in KF, which would provide valuable insights into the Al tolerance mechanisms in soybean.
Highlights
Soybean (Glycine max (L.) Merr.) is an important legume crop, supplying high-quality oil and protein for human food, animal feed, and industrial use [1,2]
The Relative root growth (RRG) of both varieties decreased with the duration of Al treatment, and the reduction was more obvious in GF (Figure 1A)
The results suggest that H2O2 pretreatment increased the POD activity in soybean roots, which might alleviate Al-induced oxidative stress, leading to improved Al tolerance (RRG) of soybean roots
Summary
Soybean (Glycine max (L.) Merr.) is an important legume crop, supplying high-quality oil and protein for human food, animal feed, and industrial use [1,2]. Al-induced oxidative stress has been reported as a prominent symptom of Al toxicity [14,15]. Excessive ROS can give rise to oxidative damage to lipid membranes, proteins and deoxynucleic acids, which eventually leads to injured or died cells [16,17]. Antioxidant enzymes might play important roles in plant tolerance to Al stress by scavenging ROS. A study shows peroxidase (POD) expression was markedly up-regulated under Al stress, and POD activities significantly increased under Al exposure in wheat roots [18]. Hydrogen peroxide (H2O2) is a key ROS that is an important signal for the activation of plant defense pathways against biotic and abiotic stresses. A previous study showed that H2O2 pretreatment increased the POD activities and total antioxidant capacity, which alleviated Al-induced oxidative stress in wheat seedlings [21]
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