Abstract
Crown roots are essential for plants to obtain water and nutrients, perceive environmental changes, and synthesize plant hormones. In this study, we identified and characterized short crown root 8 (scr8), which exhibited a defective phenotype of crown root and vegetative development. Temperature treatment showed that scr8 was sensitive to temperature and that the mutant phenotypes were rescued when grown under low temperature condition (20 °C). Histological and EdU staining analysis showed that the crown root formation was hampered and that the root meristem activity was decreased in scr8. With map-based cloning strategy, the SCR8 gene was fine-mapped to an interval of 126.4 kb on chromosome 8. Sequencing analysis revealed that the sequence variations were only found in LOC_Os08g14850, which encodes a CC-NBS-LRR protein. Expression and inoculation test analysis showed that the expression level of LOC_Os08g14850 was significantly decreased under low temperature (20 °C) and that the resistance to Xanthomonas oryzae pv. Oryzae (Xoo) was enhanced in scr8. These results indicated that LOC_Os08g14850 may be the candidate of SCR8 and that its mutation activated the plant defense response, resulting in a crown root growth defect.
Highlights
The scr8 mutant was obtained from a natural variation of indica variety R1206
The root development of scr8 was of scr8 was significantly inhibited and the plants perished in the fieldsignif(Figure 2A
To quantify the pathogen responses, the lesion lengths were measured after 15 days, and the results show that the lesion lengths of scr8 were significantly shorter than those of WT (Figure 8A–D)
Summary
Plant root systems are divided into two main types: fibrous root systems and taproot systems. Rice is a monocotyledonous plant, and its crown roots mainly undergo three stages of development: initiation, emergence, and 4.0/). Elongation, in which the abnormal development will directly affect the morphology of roots [2,3]. Root growth and development are derived from stem cells, which divide into root apical meristem (RAM) to enter the elongation/differentiation zone to initiate cell differentiation [4]. To ensure root meristem maintenance, the cell division and differentiation must be coordinated, and disturbance of the balance will affect the RAM activity, resulting in abnormal development of root length and size [4,5,6]. WOX11 encodes a WUSCHEL (WUS)-related homeobox protein that regulates crown root meristem cell proliferation by recruiting the ADA2-GCN5 histone acetyltransferase module to activate downstream target genes [7]
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