Histogen Layers Contributing to Adventitious Bud Formation Are Determined by their Cell Division Activities

Abstract

Saintpaulia ionantha is propagated by adventitious buds in horticulture, and periclinal chimeral cultivars are usually difficult to propagate. However, some periclinal chimeral cultivars can be propagated with adventitious buds, and the mechanism of which has been unknown. Striped flower cultivars “Kaname,” “Concord,” and “Monique” were used to investigate what causes flower color separation in adventitious shoot-derived plants by tissue culture. These cultivars were revealed to have mutated flavonoid 3′, 5′ hydroxylase (SiF3′5′H), WDR1 (SiWDR1), or flavonoid 3 hydroxylase (SiF3H), respectively, in their L1 layer. From our previous study using “Kaname,” all flowers from adventitious shoots were colored pink, which was the epidermal color of mother plants' flowers. We used “Concrd” and “Monique” from which we obtained not only monochromatic-colored plants the same as the epidermal color of mother plants, but also plants with a monochromatic colored plants, same as the subepidermal color, and a striped flower color the same as mother plants. Histological observations revealed that epidermal cells divided actively at 14 d after culture and they were involved in the formation of adventitious shoots in the cultured leaf segments of “Kaname.” On the other hand, in “Concord” and “Monique,” the number of divided cells in the subepidermis was rather higher than that of epidermal cells, and subepidermal cells were sometimes involved in shoot formation. In addition, the plant and leaf size of L1-derived plants from “Concord” and “Monique” were non-vigorous and smaller than those derived from the subepidermal layer. In conclusion, periclinal chimeral cultivars of Saintpaulia can be divided into two types. One type has a high cell division activity in the L1 layer, from which only single flower-colored plants derived from L1 can be obtained as adventitious shoots. Another type has a low cell division activity in the L1 layer, from which striped flower-colored plants the same as mother plants derived from several layers including L1 can be obtained as adventitious shoots. In the periclinal chimeral cultivar capable of propagation with adventitious shoots, the possibility was shown that cells in the L2 layer could form shoots by involving cells of the L1 layer with a low division activity.

Effect of Silver Nanoparticles on the In Vitro Regeneration, Biochemical, Genetic, and Phenotype Variation in Adventitious Shoots Produced from Leaf Explants in Chrysanthemum

“…The appearance of identically changed chrysanthemum mutants, in terms of inflorescence color, was also reported by Zalewska [33] and explained as the existence of some genotype-specific variation trends. On the other hand, Broertjes et al [34] pointed to the possibility of a multi-meristem formation from the initial mutated cell and, as a consequence, the growth of more than one adventitious shoot from the same adventitious meristemoid, although it is generally accepted that adventitious shoot formation occurs from a single cell in chrysanthemum [35] and in many other plant species [36].…”

Effects of the in vitro behavior of micropropagated plants on the stability of variegation in Yucca gloriosa, Phormium tenax, and Cordyline australis cultivars

“…The three variegated cultivars present bicolored leaves with a difference between the center of the limb and the leaf edges. These variegated models (cell-lineage type) are generally associated with the expression of genes differentiated according to their location on the leaf or their epigenetic instability (Marcotrigiano, 1997;Nabeshima et al, 2017), but more specifically with periclinal chimeras, i.e., plants where an entire layer of the shoot apical meristem is genetically distinct from the others (Stewart and Dermen, 1979;Marcotrigiano, 1997;Frank and Chitwood, 2016). The three layers (L1-L2-L3) of the meristem are maintained during plant development and contribute to the formation of the different organ tissues, where the L1 layer normally contributes to the epidermis, the L2 layer to one or two layers of subepidermal cells and the leaf edge mesophyll, and the L3 layer to the inner leaf blade mesophyll (Fig.…”

“…Adventitious meristem formations generally arise from a single cell in many plants (Boertjes et al, 1968;Yang et al, 2017), often with only the participation of the L1 epidermal layer (Boertjes and Van Harten, 1985;Peary et al, 1988;Yang et al, 2017). Nevertheless, histological analyses revealed that all of the cell layers can be at the origin of an adventitious meristem, with the possibility of a multicellular origin, sometimes leading, even in small proportions, to variegated plants arising from adventitious regeneration (Marcotrigiano, 1986;Nabeshima et al, 2017). The consequence is that numerous studies have shown that propagation of periclinal chimeras by axillary bud meristems maintained a chimeric structure, whereas adventitious meristems led to the reorganization of cell layers and to very low rates of true-to-type plants (Papachatzi et al, 1981;Pierik et al, 1983;Lineberger and Wanstreet, 1983;McPheeters and Skirvin, 1983;Lineberger and Druckenbrod, 1985;Marcotrigiano, 1986;Pogany and Lineberger, 1990;Marcotrigiano et al, 1997;Amory and Gill, 1999).…”

Growth and photosynthetic traits differ between shoots originated from axillary buds or from adventitious buds in Populus balsamifera L. cuttings

“…Adventitious buds may play an important role in tree response to climate change (Chao et al 2017). The meristem of an adventitious bud is believed to be derived from a single cell located in the epidermal layer or vascular cambium (Nabeshima et al 2017), different from the origin of the meristem of a terminal bud or an axillary bud; thus, shoots developed from adventitious buds may have different phenology than their parent plant (Vanden Broeck et al 2018). This phenotypic variability may improve the response of trees to climate change and heterogeneous environments (McKown et al 2014).…”