Asian soybean rust is an aggressive foliar disease caused by the obligate biotrophic fungus Phakopsora pachyrhizi. On susceptible plants, the pathogen penetrates and colonizes leaf tissue, resulting in the formation of necrotic lesions and the development of numerous uredinia. The soybean Rpp2 gene confers resistance to specific isolates of P. pachyrhizi. Rpp2-mediated resistance limits the growth of the pathogen and is characterized by the formation of reddish-brown lesions and few uredinia. Using virus-induced gene silencing, we screened 140 candidate genes to identify those that play a role in Rpp2 resistance toward P. pachyrhizi. Candidate genes included putative orthologs to known defense-signaling genes, transcription factors, and genes previously found to be upregulated during the Rpp2 resistance response. We identified 11 genes that compromised Rpp2-mediated resistance when silenced, including GmEDS1, GmNPR1, GmPAD4, GmPAL1, five predicted transcription factors, an O-methyl transferase, and a cytochrome P450 monooxygenase. Together, our results provide new insight into the signaling and biochemical pathways required for resistance against P. pachyrhizi.
Iron (Fe) is an essential micronutrient for all organisms. In crop plants, Fe deficiency can decrease crop yield significantly; however, our current understanding of how major crops respond to Fe deficiency remains limited. Herein, the effect of Fe deprivation at both the transcriptomic and metabolic level in hexaploid wheat was investigated. Genome-wide gene expression reprogramming was observed in wheat roots subjected to Fe starvation, with a total of 5854 genes differentially expressed. Homoeologue and subgenome-specific analysis unveiled the induction-biased contribution from the A and B genomes. In general, the predominance of genes coding for nicotianamine synthase, yellow stripe-like transporters, metal transporters, ABC transporters, and zinc-induced facilitator-like protein was noted. Expression of genes related to the Strategy II mode of Fe uptake was also predominant. Our transcriptomic data were in agreement with the GC-MS analysis that showed the enhanced accumulation of various metabolites such as fumarate, malonate, succinate, and xylofuranose, which could be contributing to Fe mobilization. Interestingly, Fe starvation leads to a significant temporal increase of glutathione S-transferase at both the transcriptional level and enzymatic activity level, which indicates the involvement of glutathione in response to Fe stress in wheat roots. Taken together, our result provides new insight into the wheat response to Fe starvation at the molecular level and lays the foundation to design new strategies for the improvement of Fe nutrition in crops.
HighlightThis study demonstrates the importance of the wheat ABCC transporter (TaABCC13) for achieving low phytic acid in grains, and substantiates its previously speculated role during heavy metal detoxification.
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