Organogenic responses in tissue culture of srd mutants of Arabidopsis thaliana

Abstract

In Arabidopsis thaliana, shoot redifferentiation and root redifferentiation can be induced at high frequency from hypocotyl and root explants by a two-step culture method. Tissues are precultured on callus-inducing medium and then transferred onto shoot-inducing medium for shoot redifferentiation or onto root-inducing medium for root redifferentiation. In an attempt to dissect these organogenic processes genetically, we characterized the responses in tissue culture of srd1, srd2 and srd3 mutants that were originally isolated as temperature-sensitive strains with defects in shoot redifferentiation (Yasutani, I., Ozawa, S., Nishida, T., Sugiyama, M. and Komamine, A. (1994) Plant Physiol. 105, 815–822). These mutants exhibited temperature sensitivity at different steps of organogenesis, which allowed the identification of three states associated with organogenic competence: IC (incompetent); CR (competent with respect to root redifferentiation); and CSR (competent with respect to shoot and root redifferentiation). Hypocotyl explants were shown to be in the IC state at the initiation of culture and to enter the CSR state, via the CR state, during preculture on callus-inducing medium, whereas root explants seemed to be in the CR state at the initiation of culture. The transition from IC to CR and that from CR to CSR appeared to require the functions of SRD2 and SRD3, respectively. It appears that explants in the CSR state redifferentiate shoots with the aid of the products of SRD1 and SRD2 when transplanted onto shoot-inducing medium. Histological examination of the srd mutants revealed that the function of SRD2 is required not only for organogenesis but also for the reinitiation of cell proliferation in hypocotyl explants during culture on callus-inducing medium. Linkage analysis using RFLP markers indicated that SRD1, SRD2, and SRD3 are located at the lower region, the central region, and the upper region of chromosome 1, respectively.

High auxin stimulates callus through SDG8‐mediated histone H3K36 methylation in Arabidopsis

“…Tissue culture was performed according to a published protocol (Ozawa et al, 1998; Che et al, 2002) with minor modifications.…”

“…For hypocotyl explants shoot regeneration, 1 cm hypocotyl explants cut from 5‐d‐old dark growing seedlings were incubated on CIM for 4 d, then the hypocotyls were transformed to SIM (B5 basic medium containing 5 μmol/L 2‐IP and 0.9 μmol/L IAA) for another 12 d before taking photos (Ozawa et al, 1998; Che et al, 2002).…”

Promoting genotype-independent plant transformation by manipulating developmental regulatory genes and/or using nanoparticles

“…Thus, it is easy to regenerate roots when the CIM-induced callus is transferred to RIM. Establishing the identity of root meristem and further root development can be regulated through auxin-induced transcriptional cascade (Ozawa et al 1998 ). In contrast, shoot regeneration may be more complex because it requires the transition from root meristem fate to shoot meristem fate.…”

Deciphering the transcriptomic insight during organogenesis in Castor (Ricinus communis L.), Jatropha (Jatropha curcas L.) and Sunflower (Helianthus annuus L.)

“…Christianson [19] classified the phenomenon of shoot organogenesis into three phases: acquisition of competency, identity specification and differentiation. Valvekens et al [20] studied indirect organogenesis procedure in Arabidopsis in which root explants were induced to form callus on a callus induction medium and then transferred to shoot induction medium to induce shoots wherein cells become competent to shoot induction signals on callus induction medium itself [21,22]. There is no single report for gene expression analysis (or) proteomic analysis identifying genes responsible for regeneration recalcitrance in castor.…”