A novel semi-dominant allele of the transmembrane NAC transcription factor ZmNTL2 reduces the size of multiple maize organs

Chuan Li^a,Yun Bai^a,b,Yuwei Hou^a,Siyu Wang^a, Yue Xin^a, TaoYua, Jing Wang^a,Xiaowei Liu^a,Hongyang Yi^a,Chao Xia^a,Hai Lan^a,*,Moju Cao^a,*

abstract

Maize plant architecture influences planting densityand,in turn, grainyield.Mostof the plant architecture-related traits can be described as organsize.We describe a miniature maize mutant,Tinyplant 4 (Tip4), which exhibits reduced size of multiple organs and exhibitsasemi-dominant monofacto-rial inheritance characteristic.Positional cloning confirmed that a 4-bp deletion in the NACTF with trans-membranemotif1-Like(NTL)geneZmNTL2,denotedasZmNTL2Δ,confers the Tip4 mutation.qRT-PCR showed that ZmNTL2 was expressed in all tested tissues. ZmNTL2 functions as a transcriptional activator and is located in both the nucleus and biomembranes. The mutation does not affect the mRNA abundance of ZmNTL2 locus, but it does result in the loss of transmembrane domain and confines the ZmNTL2Δproteinto the nucleus. Knocking out ZmNTL2 has no effect onmaizeorgansize development,indicating that the 4-bp deletion might be a gain-of-function mutation in organ size regulation.Combining transcriptome sequencing with cytokinin and auxin content determination suggests that the decreased organ sizemay bepossiblymediated by changes in hormonehomeostasis.

Keywords

Organ size,γ-raymutagenesis, Membrane-bound NAC TF,Hormone homeostasis,Maize