RNA interference suppression of AGAMOUS and SEEDSTICK alters floral organ identity and impairs floral organ determinacy, ovule differentiation, and seed‐hair development in Populus

Abstract

Summary The role of the floral homeotic gene AGAMOUS ( AG ) and its close homologues in development of anemophilous, unisexual catkins has not previously been studied. We transformed two RNA interference ( RNA i) constructs, PTG and its matrix‐attachment‐region flanked version MPG , into the early‐flowering female poplar clone 6K10 ( Populus alba ) to suppress the expression of its two duplicate AG orthologues. By early 2018, six out of 22 flowering PTG events and 11 out of 12 flowering MPG events showed modified floral phenotypes in a field trial in Oregon, USA . Flowers in catkins from modified events had ‘carpel‐inside‐carpel’ phenotypes. Complete disruption of seed production was observed in seven events, and sterile anther‐like organs in 10 events. Events with strong co‐suppression of both the two AG and two SEEDSTICK ( STK ) paralogues lacked both seeds and associated seed hairs. Alterations in all of the modified floral phenotypes were stable over 4 yr of study. Trees from floral‐modified events did not differ significantly ( P < 0.05) from nonmodified transgenic or nontransgenic controls in biomass growth or leaf morphology. AG and STK genes show strong conservation of gene function during poplar catkin development and are promising targets for genetic containment of exotic or genetically engineered trees.

Identification, characterization and functional analysis of AGAMOUS subfamily genes associated with floral organs and seed development in Marigold (Tagetes erecta)

“…In Petunia, simultaneous down-regulation of FBP7 and BP11 formed the seedless phenotype [18,20,41]. In addition to model plants, similar phenotypes resulting from down-regulation the D class genes were also observed in other species [2,3]. The down-regulation expression of endogenous gene STK also supported this phenotypic change (Fig.…”

“…However, in stk single mutant, only the ovule funiculus is larger than that of the wild type, and the mature seeds are not detached from the silique [24][25][26][27]. In addition, the similar phenotype changes have been reported in cultivated Grapevine (Vitis vinifera) [28] and Populus [2], indicating that STK/AGL11 has a conservative function in regulating the ovule development.…”

“…In Arabidopsis, the class C genes prevent the class A genes from functioning in inner whorl oral organs, which is clearly supported by reducing the AG expression in Arabidopsis, resulting in homeotic mutation of reproductive organs such as petal-like stamens and sepalor petal-like carpels [14][15][16]. The function of AG lineage genes has been previously characterized in other eudicot species including Chrysanthemum (Chrysanthemum morifolium) [17], Petunia (Petunia hybrida) [18], Populus (Populus trichocarpa) [2], and also in monocot species such as Rice (Oryza sativa) [19].…”

“…Flowers are the reproductive organs of a plant, which are regarded as an important morphological innovation in plant evolution. The MADS-box transcription factors are key elements in oral organ identity [1,2], fruit and seed development [3,4], and leaf and root development as well [5,6]. Based on the genetic studies, a well-known ABCDE model is introduced to explain genetic regulation in oral organ determination.…”

RNAi of AGAMOUS genes in sweetgum alters reproductive organ identity and decreases fruit persistence

“…The resulting RNAi-AG trees were planted in field conditions, and their vegetative growth was monitored across growing seasons prior to, as well as after, the onset of flowering. The vegetative effects from suppression of floral homeotic gene activity have only rarely been studied under physiological conditions relevant to growth in wild and/or cultivated environments (e.g., Lu et al, 2019).…”