Reactivation of Meristem Activity and Sprout Growth in Potato Tubers Require Both Cytokinin and Gibberellin      

Abstract

Reactivation of dormant meristems is of central importance for plant fitness and survival. Due to their large meristem size, potato (Solanum tuberosum) tubers serve as a model system to study the underlying molecular processes. The phytohormones cytokinins (CK) and gibberellins (GA) play important roles in releasing potato tuber dormancy and promoting sprouting, but their mode of action in these processes is still obscure. Here, we established an in vitro assay using excised tuber buds to study the dormancy-releasing capacity of GA and CK and show that application of gibberellic acid (GA 3 ) is sufficient to induce sprouting. In contrast, treatment with 6-benzylaminopurine induced bud break but did not support further sprout growth unless GA 3 was administered additionally. Transgenic potato plants expressing Arabidopsis (Arabidopsis thaliana) GA 20-oxidase or GA 2-oxidase to modify endogenous GA levels showed the expected phenotypical changes as well as slight effects on tuber sprouting. The isopentenyltransferase (IPT) from Agrobacterium tumefaciens and the Arabidopsis cytokinin oxidase/dehydrogenase1 (CKX) were exploited to modify the amounts of CK in transgenic potato plants. IPT expression promoted earlier sprouting in vitro. Strikingly, CKX-expressing tubers exhibited a prolonged dormancy period and did not respond to GA 3 . This supports an essential role of CK in terminating tuber dormancy and indicates that GA is not sufficient to break dormancy in the absence of CK. GA 3 -treated wild-type and CKX-expressing tuber buds were subjected to a transcriptome analysis that revealed transcriptional changes in several functional groups, including cell wall metabolism, cell cycle, and auxin and ethylene signaling, denoting events associated with the reactivation of dormant meristems.

Regulation of potato tuber sprouting

“…Since the mid-1950s, it has been known that application of GA triggers tuber sprouting (Brian et al 1955;Rappaport 1956;Rappaport et al 1957). The dormancy-releasing capacity of GA was confirmed more recently by either injecting GA below the apical bud complex or by bathing isolated tuber buds in GA 3 solution (Suttle 2004b;Hartmann et al 2011;Rentzsch et al 2012). In all these studies, treatment with bioactive GA species was able to terminate dormancy and to stimulate bud outgrowth.…”

“…therein). Nonetheless, comparison of sprouting and non-sprouting tubers suggested that ethylene-associated signals may negatively influence sprout outgrowth (Hartmann et al 2011) (see Fig. 3).…”

“…This is accompanied by structural and metabolic changes as well as by an altered level of gene expression (Ronning et al 2003;Viola et al 2007;Hartmann et al 2011). Although our knowledge with respect to molecular changes during tuber dormancy has considerably increased within the last years, the molecular mechanisms triggering tuber sprouting are still unclear.…”

Caracterización morfoagronomica de genotipos promisorios de papa criolla (solanum tuberosum l.grupo andigenum) en nariño.

“…La papa (Solanum tuberosum L.) ha sido considerada como uno de los principales cultivos agrícolas a nivel mundial en cuanto a superficie, ubicada detrás de los cereales y algunos cultivos destinados a la agroindustria, como la soya y la caña de azúcar y conjuntamente con el maíz, el trigo y el arroz, representan los cuatro rubros alimenticios básicos de la seguridad y soberanía alimentaria en variadas formas de consumo por los diferentes segmentos del mercado, ocupa un lugar importante en la agricultura, economía y seguridad alimentaria, situándose en el tercer cultivo de mayor consumo en el mundo (Hartmann et al 2011). Esta especie para su cultivo se propaga clonalmente, es mayoritariamente autotetraploide, altamente heterocigota y sufre depresión aguda por endogamia (The Potato Genome Sequencing Consortium -PGSC.…”

Mechanisms of vegetative propagation in bulbs : a molecular approach

“…However, the buds that are initiated when the shoot apical meristem (SAM) of their mother has transitioned into the reproductive state ('A and B' buds in tulip), are able to skip this kind of dormancy (Chapter 4 and (Rees 1968)). This particular dormancy is known as paradormancy and imposed by apical dominance (Lang et al 1987 (Yao and Finlayson 2015;González-Grandío et al 2017;GomezRoldan et al 2008;Liang et al 2010;Pasare et al 2013;González-Grandío and Cubas 2014;Wu et al 2015;Hartmann et al 2011). …”