Cytokinin and auxin regulates WUS induction and inflorescence regeneration in vitro in Arabidopsis

Abstract

Inflorescence regeneration in vitro provides a simplified approach for the study of inflorescence development. In this study, high frequency of regenerated inflorescences was established using Arabidopsis stage-10 pistil as the explants on the inducing medium containing the 2 mg/L zeatin and 0.01 mg/L indole-3-acetic acid. TERMINAL FLOWER 1 (TFL1) expression was detected in callus at 6 days after transferred to inducing medium, and LEAFY (LFY) expression was detectable subsequently, suggesting that both genes play important roles as they function on inflorescence development in the plant. To investigate the formation of the stem cell organizing center, we examined the WUSCHEL (WUS) and CLAVATA3 (CLV3) expression within callus during inflorescence regeneration. WUS signals start to accumulate on callus at 4 days after induction, and then, the CLV3 signals are induced on callus at 5 days on the inflorescence-inducing medium. The expression domain of WUS is below that of CLV3, indicating that the patterns of the organizing center and stem cell formation are similar to that in zygotic and somatic embryogenesis. However, more cells of the organizing center were observed within callus than pro-embryo, suggesting that inflorescence differentiation requires more cells of the organizing center. Furthermore, it was found that the WUS expression is controlled by the ratio of cytokinin with auxin. The results suggest that other factors besides WUS and CLV3 are required for inflorescence regeneration.

Pattern of Auxin and Cytokinin Responses for Shoot Meristem Induction Results from the Regulation of Cytokinin Biosynthesis by AUXIN RESPONSE FACTOR3

“…In vitro culture and shoot induction using pistils as explants were performed according to Cheng et al (2010).…”

“…Different ratios of exogenous auxin and cytokinin determine cell fates in the callus, indicating the importance of these ratios and the potential cross talk between these two hormones in pattern formation during organ regeneration. Indeed, previous results have shown that the cytokinin response is critical for de novo stem cell initiation and shoot meristem establishment in Arabidopsis (Gordon et al, 2007;Su et al, 2009;Cheng et al, 2010). Mutations of the cytokinin receptor gene ARABIDOPSIS HISTIDINE KI-NASE4 (AHK4) or type A ARABIDOPSIS RESPONSE REGULATOR7 (ARR7) and ARR15 affect the de novo shoot formation of Arabidopsis (Buechel et al, 2010).…”

Osmotic stress stimulates shoot organogenesis in callus of rice (Oryza sativa L.) via auxin signaling and carbohydrate metabolism regulation

“…Many studies have shown the effects of PGRs on tissue culture (Jiménez 2005;Yin et al 2008;Zhang et al 2008;Barreto et al 2010;Feng et al 2010;Huang et al 2012). Auxin and cytokinin are considered key factors to shoot differentiation in callus culture (Skoog et al 1965;Pernisová et al 2009;Su et al 2009;Cheng et al 2010;Vanneste and Friml 2009;Zhao et al 2010). Besides, though ABA is considered an inhibitor of plant growth, while acting with other PGRs, it has a positive effect on plantlet development (Rai et al 2011;Huang et al 2012).…”

An Efficient System for Regenerating Taraxacum Pieninicum Pawł. from Seedling Explants

“…The presence of cytokinins in the culture medium at a concentration exceeding that of auxin leads to formation of callus and adventitious bud differentiation within it (Skoog and Miller, 1957). Cytokinin triggers induction of ectopic expression of the WUS gene within the callus, and it is sufficient to induce shoot regeneration (Gordon et al, 2009;Cheng, 2010), whereas adding cytokinins to the growth medium in lateral bud culture reduces apical shoot dominance, resulting in axillary bud development (Gaspar et al, 2003;Shani et al, 2006). The shoots obtained require rooting.…”