Abstract
Axis formation is a fundamental issue in developmental biology. Axis formation and patterning in plant leaves is crucial for morphology and crop productivity. Here, we reveal the basis of proximal-distal patterning in rice leaves, which consist of a proximal sheath, a distal blade, and boundary organs formed between these two regions. Analysis of the three rice homologs of the Arabidopsis BLADE-ON-PETIOLE1 (BOP1) gene indicates that OsBOPs activate proximal sheath differentiation and suppress distal blade differentiation. Temporal expression changes of OsBOPs are responsible for the developmental changes in the sheath:blade ratio. We further identify that the change in the sheath:blade ratio during the juvenile phase is controlled by the miR156/SPL pathway, which modifies the level and pattern of expression of OsBOPs. OsBOPs are also essential for differentiation of the boundary organs. We propose that OsBOPs, the main regulators of proximal-distal patterning, control temporal changes in the sheath:blade ratio of rice leaves.
Highlights
Axis formation is a fundamental issue in developmental biology
We show that OsBOPs determine the leaf sheath: blade ratio through activation of proximal sheath differentiation and suppression of distal blade differentiation
Among three BOP homologs of rice, OsBOP1 is the closest homolog of two BOP genes in Arabidopsis, while OsBOP2 and OsBOP3 belong to a grass-specific clade (Supplementary Fig. 2)[27,28,29]
Summary
Axis formation is a fundamental issue in developmental biology. Axis formation and patterning in plant leaves is crucial for morphology and crop productivity. We propose that OsBOPs, the main regulators of proximal-distal patterning, control temporal changes in the sheath:blade ratio of rice leaves. There are two major features in proximal-distal patterning in grass leaves, namely, differentiation of distinct regions along the axis and determination of sheath:blade ratio. The boundary organs are formed between sheath and blade, the sheath and blade differentiate even in liguleless (lg) mutants in which both ligule and auricle are lost[8,9,10] This indicates that boundary organ formation and determination of the sheath:blade ratio are independently controlled aspects of proximal-distal patterning. Whether BOP genes play any roles in determination of the leaf sheath:blade ratio, the main feature of proximal-distal patterning in grass leaves, is unknown
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