Genome-Wide Analysis Of The Role Of ASR5 In Rice Aluminium Response

Aluminum (Al) toxicity in plants is one of the primary constraints in crop production. Al³⁺, the most toxic form of Al, is released into soil under acidic conditions and causes extensive plant damage, especially in the roots. Among cereal crops, rice is considered the most Al-tolerant. However, variability among rice genotypes leads to remarkable differences in the degree of Al tolerance for distinct cultivars. A number of studies have demonstrated that rice plants achieve Al tolerance through external and internal Al detoxification mechanisms and novel mechanisms to manage Al toxicity. We have analyzed expression changes of the rice ASR gene family as a function of Al treatment. The gene ASR5  is differentially regulated in the Al-tolerant rice ssp Japonica cv Nipponbare. However, ASR5 expression did not respond to Al exposure in Indica cv Taim rice roots, which are highly Al-sensitive. Transgenic plants carrying RNAi constructs that targeted the ASR genes were obtained, and increased Al susceptibility was observed in T1 plants. Using high-throughput analyses, we showed a large-scale profile of Al-responsive genes in rice. Using ASR5_RNAi plants, a global transcriptome analysis was performed to compare non-transformed and ASR-silenced plants. The results allowed the identification of several genes affected by ASR5 silencing. Chromatin immunoprecipitation, followed by deep sequencing revealed the binding motif for ASR5 and demonstrated that ASR5 can act as transcription factor in rice to regulate gene expression during Al stress.