Morphological characterization and genetic analysis of tri-pistil trait, a precisely regulated pistil number mutation in bread wheat

Abstract

Bread wheat (Triticum aestivum L.) is an important source of nutrients for humans. Therefore, improvement of its yields is essential to feed the increasing world population. The tri-pistil (TRP) trait in wheat has a high potential for increasing yields. We obtained a pure tri-pistil wheat line, 4045, and evaluated its morphological properties. The 4045 wheat line stably produced three independently inherited pistils, which led to 1-3 grains in each floret. Among the three pistils, two lately emerged pistils initiated at late anther primordia stage to early tetrads stage. Genetic analysis revealed that there were TRP penetrance variations among the 11 F1 populations of 4045. Fine mapping narrowed the single dominant TRP locus to a 97.3 kb region, containing two candidate genes, on the 2DL chromosome. However, further gene sequence, functional as well as comparative genomic analyses ruled out the only two candidate genes. Therefore, TRP is high-likely a unique gain-of-function mutation that does not exist in normal wheat genome. Transcriptome analysis of floral homeotic genes revealed that expressions of the C-class TaAG-2s, which are essential for carpel specification, significantly increased in 4045, implying that TaAG-2s have played important roles in TRP-regulated tri-pistil formation. This study highlights that TRP leads to a precisely regulated pistil number increase (PRPNI) mutations and proposed a regulatory model of PRPNI pistil architecture. PRPNI offers a novel abnormal pistil development resource for research of floral architectures and potential on crop yield improvement.

MADS8 is indispensable for female reproductive development at high ambient temperatures in cereal crops

“…Barley may share a similar FM termination mechanism as rice. Unlike the extra carpels produced in rice fon mutants and wheat tri-pistil mutants that can produce multiple grains within a single floret ( Jiang et al 2005 ; Chu et al 2006 ; Moon et al 2006 ; Suzaki et al 2006 ; Liu et al 2022 ), extra carpels in Hvmads8 florets form at the expense of ovules at high temperatures ( Fig. 2A ), indicating a close link between ovule initiation and FM determinacy during the floral developmental program.…”

“…FLORAL ORGAN NUMBER ( FON ) genes in rice control FM size, and loss-of-function fon mutants produce larger meristems with supernumerary anthers and pistils that can produce grain ( Jiang et al 2005 ; Chu et al 2006 ; Moon et al 2006 ; Suzaki et al 2006 ). Florets from tri-pistil mutants in wheat ( Triticum aestivum ) produce 3 pistils that occasionally contain multiple ovules and generate 1 to 3 grains in a single floret ( Peng et al 2008 ; Li et al 2020 ; Liu et al 2022 ). The 2 extra pistils appear to be initiated late in floret development, and anthers are retained, suggesting that the tri-pistil phenotype may relate to meristem determinacy ( Nagasawa et al 2003 ; Li et al 2020 ; Selva et al 2021 ; Liu et al 2022 ).…”

“…Florets from tri-pistil mutants in wheat ( Triticum aestivum ) produce 3 pistils that occasionally contain multiple ovules and generate 1 to 3 grains in a single floret ( Peng et al 2008 ; Li et al 2020 ; Liu et al 2022 ). The 2 extra pistils appear to be initiated late in floret development, and anthers are retained, suggesting that the tri-pistil phenotype may relate to meristem determinacy ( Nagasawa et al 2003 ; Li et al 2020 ; Selva et al 2021 ; Liu et al 2022 ).…”