LMI1-like and KNOX1 genes coordinately regulate plant leaf development in dicotyledons

Lijing Chang,Jieqiong Deng,Tianzhen Zhang,Yan Hu,Gaofu Mei

doi:10.1007/s11103-019-00829-7

Lijing Chang, Jieqiong Deng + Show 3 more

Open Access

https://doi.org/10.1007/s11103-019-00829-7

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Abstract

Key messageThis report reveals that the LMI1-like and KNOX1 genes coordinately control the leaf development and different combinations of those genes which produce diverse leaf shapes including broad, lobed and compound leaves.Class I KNOTTED1-like homeobox (KNOX1) genes are involved in compound leaf development and are repressed by the ASYMMETRIC LEAVES1 (AS1)–AS2 complex. Cotton plants have a variety of leaf shapes, including broad leaves and lobed leaves. GhOKRA, a LATE MERISTEM IDENTITY 1 (LMI1)-like gene, controls the development of an okra leaf shape. We cloned the corresponding cotton homologs of Arabidopsis thaliana AS1 and AS2 and seven KNOX1 genes. Through virus-induced gene silencing technology, we found that either GhAS1 or GhAS2-silenced cotton plants showed a great change in leaf shape from okra leaves to trifoliolate dissected leaves. In the shoot tips of these plants, the expression of the cotton ortholog of Knotted in A. thaliana 1 (KNAT1), GhKNOTTED1-LIKE2/3/4 (GhKNL2/3/4), was increased. However, GhKNOX1s-silenced plants maintained the wild-type okra leaves. A novel dissected-like leaf in A. thaliana was further generated by crossing plants constitutively expressing GhOKRA with either as1-101 or as2-101 mutant plants. The dissected-like leaves showed two different leaf vein patterns. This report reveals that the LMI1-like and KNOX1 genes coordinately control leaf development, and different combinations of these genes produce diverse leaf shapes including broad leaves, lobed leaves and compound leaves. This is the first report on the artificial generation of compound leaves from simple leaves in cotton.

Highlights

Plant leaves are initiated from the peripheral region of the shoot apical meristem (SAM), and display great variations in shape and size
The deeply lobed leaves in the okra leaf cotton were replaced by ternate compound leaves; a phenomenon that has not been observed before in cotton. Quantitative real time PCR (qPCR) analysis showed that the expression of GhAS1 and GhAS2 was lower in pTRV2-GhAS1 and pTRV2-GhAS2silenced lines compared to controls (Fig. 3b)
These results demonstrate that GhAS1 and GhAS2 regulate the depth of leaf lobes in cotton

Summary

Introduction

Plant leaves are initiated from the peripheral region of the shoot apical meristem (SAM), and display great variations in shape and size. They are traditionally classified into two major morphogenetic classes: undivided simple leaves, and compound leaves. Plant Molecular Biology (2019) 99:449–460 for example, unlobed leaves in Arabidopsis and broad or lobed leaves in cotton (Fig. 1a–c). Many compound leaf mutants in Cardamine hirsuta and Medicago truncatula have defective separation between the adjacent leaflets leading to the conversion of dissected leaves into lobed simple leaves (Peng et al 2011; Vlad et al 2014). Lobed simple leaves are essentially an intermediate shape between serrations and dissected leaves. Whether gene mutations can cause lobed leaves to become compound leaves requires further investigation

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