Background: Node is the central organ of transferring nutrients and ions in plants. Cadmium (Cd) induced crop pollution threatens the food safety. Breeding of low Cd accumulation cultivar 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 (low Cd accumulation cultivar) and Yuzhenxiang (high Cd accumulation cultivar). 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 4535 DEGs and 70 miRNAs between the two cultivars. Most genesrelated to the “transporter activity”, such as OsIRT1, OsNramp5, OsVIT2, OsNRT1.5A, and OsABCC1, play roles in blocking the upward transport of Cd. Among the genes related to “response to stimulus”, we identified OsHSP70 and OsHSFA2d/B2c in Xiangwanxian No. 12, but not in Yuzhenxiang, were all down-regulated by Cd stimulus. The up-regulation of miRNAs (osa-miR528 and osa-miR408) in Xiangwanxian No. 12 played a potent role in lowering Cd accumulation via down regulating the expression of candidate genes, such as bZIP, ERF, MYB, SnRK1 and HSPs. 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 Cd stress response.

Salt stress has the most severe impact on plant growth and development, including seed germination. However, little is known about the mechanism of NR (nitrate reductase)-associated nitric oxide (NO) regulates salt tolerance during seed germination in rice. Herein, we shown that inhibition of seed germination by salt stress was significantly impaired by sodium nitroferricyanide (SNP), a NO donor. Then a triple mutant, nr1/nr2/nr3, was generated. Results shown that germination of triple mutants were delayed and were much more sensitive to salt stress than WT plant, which can be rescued by application of SNP. qPCR analysis revealed that expressions of abscisic acid (ABA) catabolism gene, OsABA8ox1, was suppressed in triple mutants under salt stress, resulting in an elevated ABA content. Similar to SNP, application of nitrate also rescued seed germination under salt stress, which, however, was blocked in the triple mutants. Further study revealed that a nitrate responsive transcript factor, OsNLP2, was induced by salt stress, which thus up-regulates the expression of OsNRs and NR activity, resulting in promoted salt tolerance during seed germination. In addition, nitrate-mediated salt tolerance was impaired in mutant of aba8ox1, a target gene for NLP2. Transient trans-activation assays further revealed NLP2 can significantly activate the expression of OsABA8ox1 and OsNR1, suggesting that NLP2 activates expression of ABA catabolism gene directly or indirectly via NR-associated NO. Taken together, our results demonstrate that NLP2-NR associated NO was involved in salt response by increasing ABA catabolism during seed germination and highlight the importance of NO for stress tolerance of plants.

Saline‐alkali stress is one of the major abiotic stresses that severely affect rice yield. However, the mechanism by which saline‐alkali stress regulates grain filling in rice is still unclear. In this study, Oryza sativa L. spp. Indica cultivar Chaoyou1000 (C1000) was exposed to post‐anthesis saline‐alkali conditions at 6 days after anthesis, which significantly reduced the grain weight by suppressing the accumulation of starch and non‐structural carbohydrates in grains. Further analysis found that 1‐aminocyclopropane‐1‐carboxylate (ACC), a precursor for ethylene, was increased by saline‐alkali treatment. qRT‐PCR results showed that several key genes involved in ethylene biosynthesis, including the OsACS and OsACO genes, were upregulated in saline‐alkali‐treated grains. In addition, genes involved in the ethylene signalling pathway were also induced by saline‐alkali stress. Exogenous ethylene application reduced grain weight and both starch and NSC contents in grains of C1000, suggesting that saline‐alkali‐induced ethylene has a negative effect on grain filling. Furthermore, the gene expression levels of OsSUS, OsAGPL, OsAGPS, OsSSI and OsSSIIIa, which are key genes in the starch biosynthesis pathway, were downregulated in saline‐alkali‐treated grains. In agreement, assays on these enzymes further revealed that saline‐alkali stress decreased the activities of sucrose synthase (SUS), adenosine diphosphate glucose pyrophosphorylase (AGP) and starch synthase (StS). Together, our results indicated that saline‐alkali stress suppressed the enzyme activities involved in the conversion of sucrose to starch by elevating ethylene production, which led to inhibition of grain filling.

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.

Background: Node is the central organ of transferring nutrients and ions in plants. Cadmium (Cd) induced crop pollution threatens the food safety. Breeding of low Cd accumulation cultivar 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 (low Cd accumulation cultivar) and Yuzhenxiang (high Cd accumulation cultivar). 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 DEGs and 70 miRNAs between the two cultivars. Most genes related to the “transporter activity”, such as OsIRT1 , OsNramp5, OsVIT2 , OsNRT1.5A, and OsABCC1 , play roles in blocking the upward transport of Cd. Among the genes related to “response to stimulus”, we identified OsHSP70 and OsHSFA2d/B2c in Xiangwanxian No. 12 , but not in Yuzhenxiang , were all down-regulated by Cd stimulus. The up-regulation of miRNAs ( osa-miR528 and osa-miR408 ) in Xiangwanxian No. 12 played a potent role in lowering Cd accumulation via down regulating the expression of candidate genes, such as bZIP , ERF , MYB , SnRK1 and HSPs . 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 Cd stress response.

Background: Node is the central organ of transferring nutrients and ions in plants. Cadmium (Cd) induced crop pollution threatens the food safety. Breeding of low Cd accumulation cultivar 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 (low Cd accumulation cultivar) and Yuzhenxiang (high Cd accumulation cultivar). 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 DEGs and 70 miRNAs between the two cultivars. Most genes related to the “transporter activity”, such as OsIRT1 , OsNramp5, OsVIT2 , OsNRT1.5A, and OsABCC1 , play roles in blocking the upward transport of Cd. Among the genes related to “response to stimulus”, we identified OsHSP70 and OsHSFA2d/B2c in Xiangwanxian No. 12 , but not in Yuzhenxiang , were all down-regulated by Cd stimulus. The up-regulation of miRNAs ( osa-miR528 and osa-miR408 ) in Xiangwanxian No. 12 played a potent role in lowering Cd accumulation via down regulating the expression of candidate genes, such as bZIP , ERF , MYB , SnRK1 and HSPs . 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 Cd stress response.