SUMMARYLateral roots (LRs) are critical to root system architecture development in plants. Although the molecular mechanisms by which auxin regulates LR development have been extensively studied, several additional regulatory systems are hypothesized to be involved. Recently, the regulatory role of very long chain fatty acids (VLCFAs) has been shown in LR development. Our analysis showed that LTPG1 and LTPG2, transporters of VLCFAs, are specifically expressed in the developing LR primordium (LRP), while the number of LRs is reduced in the ltpg1/ltpg2 double mutant. Moreover, late LRP development was hindered when the VLCFA levels were reduced by the VLCFA synthesis enzyme mutant, kcs1‐5. However, the details of the regulatory mechanisms of LR development controlled by VLCFAs remain unknown. In this study, we propose a novel method to analyze the LRP development stages with high temporal resolution using a deep neural network and identify a VLCFA‐responsive transcription factor, MYB93, via transcriptome analysis of kcs1‐5. MYB93 showed a carbon chain length‐specific expression response following treatment of VLCFAs. Furthermore, myb93 transcriptome analysis suggested that MYB93 regulated the expression of cell wall organization genes. In addition, we also found that LTPG1 and LTPG2 are involved in LR development through the formation of root cap cuticle, which is different from transcriptional regulation by VLCFAs. Our results suggest that VLCFA is a regulator of LRP development through transcription factor‐mediated regulation of gene expression and the transportation of VLCFAs is also involved in LR development through root cap cuticle formation.
Lateral roots (LRs) are critical to rhizosphere development in plants. Although the molecular mechanisms by which auxin regulates LR development has been studied extensively, many additional regulatory systems are thought to be involved. Based on the expression analysis of LTPG1 and 2, we found that they were specifically expressed at the developing LR primordium (LRP), and the number of LRs were reduced in these mutants. Because LTPG is a protein that transports Very Long Chain Fatty Acids (VLCFAs), we hypothesized that VLCFAs regulated LR development. We revealed that late LRP development was stunted when VLCFA levels were reduced in the synthetic mutant, kcs1-5. In this study, we established a method to analyze the LRP development stages with high temporal resolution using a deep neural network. We identified a VLCFA responsible transcription factor, MYB93, from transcriptome analysis of kcs1-5. Interestingly, MYB93 showed a carbon chain length-specific expression response after treatment of VLCFA. Furthermore, myb93 transcriptome analysis suggested that MYB93 regulated the expression of cell wall organization genes. Our results indicated that VLCFA is a regulator of LRP development through transcription factor-mediated regulation of gene expression.
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