Transcriptome analysis reveals the roles of stem nodes in cadmium transport to rice grain

Abstract

Background: Node is the central organ of xylem to phloem transfer of nutrients and ions in plants. Cadmium (Cd)-induced crop pollution threatens food safety. Breeding cultivar with low Cd accumulation is a chance to resolve this universal problem. This study was performed to identify tissue specific genes involved in Cd accumulation in different rice stem nodes. Panicle node and the first node under panicle (node I) were sampled in two rice cultivars: Xiangwanxian No. 12 with low Cd accumulation and Yuzhenxiang with high Cd accumulation in the grains. RNA-seq analysis was performed to identify differentially expressed genes (DEGs) and microRNAs. Results: Xiangwanxian No. 12 had lower Cd concentration in panicle node, node I and grain compared with Yuzhenxiang , and node Ⅰ had the highest Cd concentration in the two cultivars. RNA seq analysis identified 4,535 differentially expressed genes and 70 miRNAs between the two cultivars. Most genes ( OsIRT1 , OsNramp5, OsVIT2 , OsNRT1.5A, and OsABCC1 ) related to the “transporter activity” blocked the transport of Cd up to panicle and accumulation in grains of low Cd-accumulative cultivar. Among the genes related to “response to stimulus”, we identified OsHSP70 and OsHSFA2d/B2c in “X”, but not in “y”, were all down-regulated by Cd stimulus. The up-regulation of miRNAs ( osa-miR528 and osa-miR408 ) played a potent role in lowering Cd accumulation via down regulation of genes, such as bZIP , ERF , MYB , SnRK1 and HSPs in Xiangwanxian No. 12 cultivar. Conclusions: Both panicle node and node I of Xiangwanxian No. 12 played a key role in blocking the upward transportation of Cd, while node I played a critical role in Yuzhenxiang . Distinct expression patterns of various transporter genes such as OsNRT1.5A, OsNramp5, OsIRT1, OsVIT2 and OsABCC1 resulted in differential Cd accumulation in different nodes. Likewise, distinct expression patterns of these transporter genes are likely responsible for the low Cd accumulation in Xiangwanxian No. 12 cultivar . MiRNAs drove multiple transcription factors, such as OsbZIPs, OsERFs, OsMYBs , to play a role in stress response, which contribute to the response to Cd stress in rice.

Transcriptomics of different tissues of blueberry and diversity analysis of rhizosphere fungi under cadmium stress

“…Cotton responded to cadmium stress by increasing cell wall thickness, antioxidant activity and detoxification. It has been reported that the genes involved in preventing transport of Cd to rice grains include OsIRT1 , OsNramp 5, OsVIT2 , OsNRT1.5a and OsABCC1 [ 42 ]. Transcriptome analysis of the leaves and roots of Broussonetia papyrifera showed that Cd stress affected 47 KEGG pathways, mainly involving bHLH , MYB and other important transcription factors, plant–pathogen interactions, phenylpropanoid biosynthesis, plant hormone signal transduction, and other protein synthesis and metabolism processes [ 43 ].…”