KIL1 terminates fertility in maize by controlling silk senescence

Abstract

Plant flowers have a functional life span during which pollination and fertilization occur to ensure seed and fruit development. Once flower senescence is initiated, the potential to set seed or fruit is irrevocably lost. In maize, silk strands are the elongated floral stigmas that emerge from the husk-enveloped inflorescence to intercept airborne pollen. Here we show that KIRA1-LIKE1 (KIL1), an ortholog of the Arabidopsis NAC (NAM (NO APICAL MERISTEM), ATAF1/2 (Arabidopsis thaliana Activation Factor1 and 2) and CUC (CUP-SHAPED COTYLEDON 2)) transcription factor KIRA1, promotes senescence and programmed cell death (PCD) in the silk strand base, ending the window of accessibility for fertilization of the ovary. Loss of KIL1 function extends silk receptivity and thus strongly increases kernel yield following late pollination. This phenotype offers new opportunities for possibly improving yield stability in cereal crops. Moreover, despite diverging flower morphologies and the substantial evolutionary distance between Arabidopsis and maize, our data indicate remarkably similar principles in terminating floral receptivity by PCD, whose modulation offers the potential to be widely used in agriculture.

NACs, generalist in plant life

“…In the Japanese morning glory ( Ipomoea nil ), InEPH1 is regulated by the ethylene pathway factor InEIN2 through an unknown molecular mechanism and regulates downstream PCD genes involved in accelerated flower senescence (Shibuya et al ., 2014). In maize, KIL1, an ortholog of the Arabidopsis NAC TF KIRA1, accelerates the senescence of maize filaments through PCD to terminate flower pollination (Šim Škov et al ., 2022). In tulips, the overexpression of TgNAP accelerates petal senescence, whereas silencing TgNAP delays senescence.…”

Maize stigmas react differently to self-/cross-pollination and fungal invasion

“…Previous studies have reported that maize silks undergo an accelerated process of senescence in response to compatible pollination (Bassetti and Westgate 1993; Sella Kapu and Cosgrove 2010; Šimášková, et al 2022). Thus, we searched for senescence-associated genes within the differentially expressed genes in maize silks as a result of compatible pollination.…”

A scalable phenotyping approach for female floral organ development and senescence in the absence of pollination in wheat

“…Despite the conserved overall patterns, we identified differences in the duration of the growth, peak and deterioration phases in the three wheat MS cultivars used here. Gene expression studies of unpollinated carpels and stigma in Arabidopsis and maize ( Carbonell-Bejerano et al, 2010 ; Gao et al, 2018 ; Šimášková et al, 2022 ) have demonstrated that the lifespans of these floral structures are controlled by transcription factors that regulate developmental programmed cell death in these tissues. Here, we also identified distinct waves of expression of genes encoding senescence-associated TFs across late stigma development in a single wheat MS cultivar.…”