Abstract
Lodging is the primary factor limiting high yield under a high plant density. However, an optimal plant height and leaf shape can effectively decrease the lodging risk. Here we studied an ethyl methanesulfonate (EMS)-induced dwarf and a narrow-leaf mutant, dnl2. Gene mapping indicated that the mutant was controlled by a gene located on chromosome nine. Phenotypic and cytological observations revealed that dnl2 showed inhibited cell growth, altered vascular bundle patterning, and disrupted secondary cell wall structure when compared with the wild-type, which could be the direct cause of the dwarf and narrow-leaf phenotype. The phytohormone levels, especially auxin and gibberellin, were significantly decreased in dnl2 compared to the wild-type plants. Transcriptome profiling of the internodes of the dnl2 mutant and wild-type revealed a large number of differentially expressed genes enriched in the cell wall biosynthesis, remodeling, and hormone biosynthesis and signaling pathways. Therefore, we suggest that crosstalk between hormones (the altered vascular bundle and secondary cell wall structure) may contribute to the dwarf and narrow-leaf phenotype by influencing cell growth. These results provide a foundation for DNL2 gene cloning and further elucidation of the molecular mechanism of the regulation of plant height and leaf shape in maize.
Highlights
Maize (Zea mays L.) is one of the most important cereal crops in the world
Significant reductions in plant height and ear height were observed in the dnl2 mutant when compared to the wild-type, with 71% and 65% reductions observed at the mature stage, respectively (Figure 1A,F)
Our results showed that the internode number of dnl2 was similar to that of the wild-type, while all of the internodes were significantly shortened (Figure 2)
Summary
Maize (Zea mays L.) is one of the most important cereal crops in the world. Studies have demonstrated that increasing the planting density is an essential approach in order to increase per-hectare yield potential in maize [1]. Plant height and leaf shape are important plant architecture traits that are closely associated with the lodging resistance, photosynthesis, and grain yield of maize [4]. With the popularization of short stature varieties during the green revolution, the yield of rice and wheat has increased sharply since the 1960s [5]. Leaf shape parameters, such as leaf length, leaf width, and leaf area, are important components of leaf morphology that affect canopy structure, photosynthetic efficiency, and wind circulation under high planting density [6]. Understanding the genetic mechanisms of maize plant height and leaf shape are important for the breeding of density-tolerant maize varieties with high grain yield
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