Proper gibberellin localization in vascular tissue is required to regulate adventitious root development in tobacco

Abstract

Bioactive gibberellins (GAs) are involved in many developmental aspects of the life cycle of plants, acting either directly or through interaction with other hormones. Accumulating evidence suggests that GAs have an important effect on root growth; however, there is currently little information on the specific regulatory mechanism of GAs during adventitious root development. A study was conducted on tobacco (Nicotiana tabacum) plants for altered rates of biosynthesis, catabolism, and GA signalling constitutively or in specific tissues using a transgenic approach. In the present study, PtGA20ox, PtGA2ox1, and PtGAI were overexpressed under the control of the 35S promoter, vascular cambium-specific promoter (LMX5), or root meristem-specific promoter (TobRB7), respectively. Evidence is provided that the precise localization of bioactive GA in the stem but not in the roots is required to regulate adventitious root development in tobacco. High levels of GA negatively regulate the early initiation step of root formation through interactions with auxin, while a proper and mobile GA signal is required for the emergence and subsequent long-term elongation of established primordia. The results demonstrated that GAs have an inhibitory effect on adventitious root formation but a stimulatory effect on root elongation.

In vitro plant regeneration from nodal segments of the spontaneous F1 hybrid Santalum yasi × S. album and its parents S. album and S. yasi

“…GA 3 plays an important role in seed germination and cotyledon lengthening (Niu et al 2013;Ribeiro et al 2015). Rugkhla and Jones (1998) showed that GA 3 alone resulted in about 10-20 % abnormal germination of SEs when mature S. album SEs originating from nodal segments were transferred onto MS medium, and 20-76 % of cultures formed abnormal SEs in the presence of 17.32 lM GA with 4.44 lM BA, or 17.32 lM GA with 4.44 lM BA and 5.71 lM IAA.…”

The auxin receptor TIR1 homolog (PagFBL 1) regulates adventitious rooting through interactions with Aux/IAA28 in Populus

“…Phytohormones are the most important modulators of AR development (Bellini et al ., ). Plant hormones, such as abscisic acid (Da Costa et al ., ; Mehrotra et al ., ), cytokinin (Della Rovere et al ., ), ethylene (Muday et al ., ; Negi et al ., ), gibberellin (Mauriat et al ., ; Niu et al ., ), jasmonic acid (Da Costa et al ., ) and strigolactones (Rasmussen et al ., ; Sun et al ., ), form a signalling network influencing cell fate determination and specification in which auxin plays the crucial role (Da Costa et al ., ; Pacurar et al ., ; Pop et al ., ). Early in the 1930s, indole‐3‐acetic acid (IAA) was shown to be effective in promoting the formation of AR primordia (Thimann and Koepfli, ), and since then IAA has been widely used to induce AR formation in the clonal propagation of various tree species, including poplar (Preece, ; Rademacher et al ., ).…”

Adventitious root formation in Arabidopsis : underlying mechanisms and applications

“…However, the question is how similar are the processes of root formation in hypocotyl and root explants. Previous findings have highlighted the similar response of hypocotyl and root explants to different hormones including strigolactone (Koltai et al, 2010;Rasmussen et al, 2012bRasmussen et al, , 2013, CK (Della Rovere et al, 2013) and gibberellic acid (Lo et al, 2008;Niu et al, 2013). Additionally, similar molecular factors have been revealed in both processes (Verstraeten et al, 2014 and references therein).…”

“…An ectopic increase of GA production in the stem of tobacco and rice reduces AR induction (Lo et al, 2008;Niu et al, 2013). Similarly, poplar mutants deficient in GA biosynthesis produced more ARs (Busov et al, 2006).…”

“…This consequently reduces auxin availability required for the induction of cell division (Mauriat et al, 2014;Niu et al, 2013). Despite its negative effect, GA was shown to promote AR formation through interactions with ethylene in deep water rice (Steffens et al, 2006).…”