Conserved and novel responses to cytokinin treatments during flower and fruit development in Brassica napus and Arabidopsis thaliana

Abstract

Hormones are an important component in the regulatory networks guiding plant development. Cytokinins are involved in different physiological and developmental processes in plants. In the model plant Arabidopsis thaliana, cytokinin application during gynoecium development produces conspicuous phenotypes. On the other hand, Brassica napus, also known as canola, is a crop plant belonging to the Brassicaceae family, as A. thaliana. This makes B. napus a good candidate to study whether the cytokinin responses observed in A. thaliana are conserved in the same plant family. Here, we observed that cytokinin treatment in B. napus affects different traits of flower and fruit development. It increases ovule and seed number, affects stamen filament elongation and anther maturation, and causes a conspicuous overgrowth of tissue in petals and gynoecia. Furthermore, cytokinin recovers replum development in both wild type B. napus and in the A. thaliana rpl ntt double mutant, in which no replum is visible. These results indicate both conserved and novel responses to cytokinin in B. napus. Moreover, in this species, some cytokinin-induced phenotypes are inherited to the next, untreated generation, suggesting that cytokinins may trigger epigenetic modifications.

The Importance of Cytokinins during Reproductive Development in Arabidopsis and Beyond

“…During this process, the two inner and outer integuments surrounding the developing female germline develop and after three rounds of mitosis, the FM gives rise to the FG in a process called megagametogenesis (Figure 2a). Moreover, it has been also reported for other Brassicaceae species that CKs influence ovule number, suggesting that the genetic manipulation of CK metabolism is a potentially powerful tool to enhance seed yield [19,22]. Intriguingly, however, it was recently demonstrated that high levels of CKs in ckx7 mutants inhibited fruit elongation [23].…”

“…By contrast, increased levels of CKs in ckx3ckx5 double mutant lead to an increase in gynoecium size and to the formation of more ovules, due to increased meristematic activity of the placenta tissue [20,21]. Moreover, it has been also reported for other Brassicaceae species that CKs influence ovule number, suggesting that the genetic manipulation of CK metabolism is a potentially powerful tool to enhance seed yield [19,22]. Intriguingly, however, it was recently demonstrated that high levels of CKs in ckx7 mutants inhibited fruit elongation [23].…”

“…Exogenous CK application in B. napus causes a reduction in stamen length and anthers that do not mature uniformly, such that few produce pollen. However, the pollen was not able to reach the stigma due to the short length of the filament, causing sterility [22]. On the contrary, during maize (Zea mays) reproductive development, male-sterile plants can also be obtained following the ectopic accumulation of CKX.…”

A copia-like retrotransposon insertion in the upstream region of the SHATTERPROOF1 gene, BnSHP1.A9, is associated with quantitative variation in pod shattering resistance in oilseed rape

“…The activity of valve margin identity genes is repressed by FRUITFULL ( FUL ) in the valves ( Gu et al , 1998 ), and REPLUMLESS ( RPL ) in the replum ( Roeder et al , 2003 ). Several phytohormones such as auxin, cytokinin, and gibberellin are also essential for pod development and the expression of valve margin identity and IND genes ( Arnaud et al , 2010 ; Marsch-Martínez et al , 2012 ; Larsson et al , 2014 ; Simonini et al , 2017 ; Zuñiga-Mayo et al , 2018 ; Sara et al , 2019 ). Braatz et al (2018 a , b ) have shown that mutations in IND and ALC homologs are linked with pod shatter resistance in oilseed rape.…”

Jasmonate and Ethylene-Regulated Ethylene Response Factor 22 Promotes Lanolin-Induced Anthocyanin Biosynthesis in ‘Zaosu’ Pear (Pyrus bretschneideri Rehd.) Fruit

“…It has since been used as a carrier for plant growth regulators in many studies on the physiological responses of plants, such as during parthenocarpy [29], fruit development [30], and the rooting of cuttings [31], with pure lanolin treatments serving as negative controls in these studies. Lanolin alone has no significant physiological effects on some plant tissues, such as roots [32], stems [33], leaves [34], and flowers [35]. However, lanolin can affect other plant tissues sometimes.…”