Abstract
Phosphorus (P) is an essential macronutrient required for plant growth and development. The involvement of cytokinin response factors (CRFs) in phosphate (Pi) homeostasis and lateral root (LR) initiation in Arabidopsis has been revealed. However, little is known in oil crops. Here, we performed genome-wide dissection of the CRF family in Brassica napus to identify 44 members, which were evolutionally classified into 6 subgroups. Among them, four BnaCRF8 genes were strongly upregulated by P deprivation, and were selected to be further investigated. Time course qRT-PCR analyses showed that four BnaCRF8 genes were enhanced dramatically after 12 h of P stress. Analyses of the subcellular localization in tobacco leaves indicated that BnaA7.CRF8 and BnaC2.CRF8 were localized in the nucleus. The expression of BnaCRF8 genes had constant negative effects on primary root growth and LR initiation and growth, and it reduced Pi acquisition and plant growth in Arabidopsis. Moreover, the expression of Pi homeostasis-related genes was modulated in BnaA7.CRF8 overexpression plants. These results suggest that BnaCRF8 genes might negatively regulate root architecture and plant growth through transcriptional modification of Pi homeostasis-related components. Overall, this study suggests that upregulation of BnaCRF8 genes might be a smart adaptive strategy to cope with continuous Pi deficiency in the environment.
Highlights
Phosphorus (P) is an essential macronutrient required for plant growth and development
The LOW PHOSPHATE ROOT1/2 (LPR1/2) genes, which encode multicopper oxidases, have been identified as important regulators of meristem responses to low Pi availability in the primary root (PR) of Arabidopsis [12], while the PHOSPHATE ROOT DEVELOPMENT (PRD) gene is involved in the regulation of root architectural responses to Pi starvation by controlling PR and lateral root (LR) elongation [13]
To obtain the cytokinin response factors (CRFs) family transcription factors (TFs) in B. napus, we used the CRF protein sequences identified in the Arabidopsis genome to perform a BLASTP search against the B. napus genome
Summary
Phosphorus (P) is an essential macronutrient required for plant growth and development. Many Pi starvation responsive transcription factors (TFs), such as PHOSPHATE STARVATION RESPONSE1 (PHR1) and PHR1-Like (PHL1), have been identified and shown to positively or negatively regulate several subsets involved in Pi homeostasis, as well as in root architecture modulation [3,14,15]. The CRF genes in Brassica crops, including B. napus, have been identified and their evolutionary relationship has been discussed [22], the Pi homeostasis-related CRF genes in B. napus have not been assessed. Their molecular function in plant Pi homeostasis remains unknown. Our work provides a comprehensive insight into the effects of BnaCRF genes on Pi homeostasis
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