TCP5 controls leaf margin development by regulating the KNOX and BEL-like transcription factors in Arabidopsis

Development of leaf margins is an important process in leaf morphogenesis. CIN-clade TCP (TEOSINTE BRANCHED1/CYCLOIDEA/PCF) transcription factors have redundant roles in specifying leaf margins, but the specific mechanisms that individual TCP genes function through remain elusive. Here we report that the CIN-TCP gene TCP5 represses the initiation and outgrowth of leaf serrations by activating two key regulators of margin development, the Class II KNOX factor KNAT3 and BEL-like gene SAW1. Specifically, TCP5 directly promotes the transcription of KNAT3 and indirectly activates the expression of SAW1.Furthermore, we also show that TCP5 regulates KNAT3 and SAW1 in a temporal and spatial specific manner that is largely in accordance with the progress of serration formation. This regulation may serve as a key mechanism to pattern margin morphogenesis and sculpt the final form of the leaf.

TB1: from domestication gene to tool for many trades

This article comments on: Dixon LE, Pasquariello M, Boden SA. 2020. TEOSINTE BRANCHED1 regulates height and stem internode length in bread wheat. Journal of Experimental Botany 71, 4742–4750.

TEOSINTE BRANCHED1 regulates height and stem internode length in bread wheat

Regulation of plant height and stem elongation has contributed significantly to improvement of cereal productivity by reducing lodging and improving distribution of assimilates to the inflorescence and grain. In wheat, genetic control of height has been largely contributed by the Reduced height-1 alleles that confer gibberellin insensitivity; the beneficial effects of these alleles are associated with less favourable effects involving seedling emergence, grain quality, and inflorescence architecture that have driven new research investigating genetic variation of stem growth. Here, we show that TEOSINTE BRANCHED1 (TB1) regulates height of wheat, with TB1 being expressed at low levels in nodes of the main culm prior to elongation, and increased dosage of TB1 restricting elongation of stem internodes. The effect of TB1 on stem growth is not accompanied by poor seedling emergence, as transgenic lines with increased activity of TB1 form longer coleoptiles than null transgenic controls. Analysis of height in a multiparent mapping population also showed that allelic variation for TB1 on the B genome influences height, with plants containing the variant TB-B1b allele being taller than those with the wild-type TB-B1a allele. Our results show that TB1 restricts height and stem elongation in wheat, suggesting that variant alleles that alter the expression or function of TB1 could be used as a new source of genetic diversity for optimizing architecture of wheat in breeding programmes.

Identification of the TCP (Teosinte Branched1/Cycloidea/Proliferating Cell Factor) gene family in Passiflora organensis

Plant development is generally controlled by a balance between hormonal influences and the action of transcription factors. Knowing the expression pattern of key genes is essential for the understanding of plant development. The TCP gene family members are tought to be involved in key events of plant development. There are reports in the literature that variations in the expression patterns of TCP genes contributed to the emergence of evolutionary novelties such as zigomorphic flowers and tendrils. The genome of Passiflora organensis is completely sequenced and allows the identification and analysis of genes potentially involved in the control of the development of plants from the genus Passiflora.