Auxin synthesis gene tms1 driven by tuber-specific promoter alters hormonal status of transgenic potato plants and their responses to exogenous phytohormones

Abstract

Ectopic auxin overproduction in transgenic potato leads to enhanced productivity accompanied with concerted and occasional changes in hormonal status, and causing altered response of transformants to exogenous auxin or cytokinin. Previously, we generated potato transformants expressing Agrobacterium-derived auxin synthesis gene tms1 driven by tuber-specific patatin gene promoter (B33-promoter). Here, we studied the endogenous hormonal status and the response to exogenous phytohormones in tms1 transformants cultured in vitro. Adding indole-3-acetic acid (IAA) or kinetin to culture medium affected differently tuberization of tms1-transformed and control plants, depending also on sucrose content in the medium. Exogenous phytohormones ceased to stimulate the tuber initiation in transformants at high (5-8%) sucrose concentration, while in control plants the stimulation was observed in all experimental settings. Furthermore, exogenous auxin partly inhibited the tuber initiation, and exogenous cytokinin reduced the average tuber weight in most transformants at high sucrose content. The elevated auxin level in tubers of the transformants was accompanied with a decrease in content of cytokinin bases and their ribosides in tubers and most shoots. No concerted changes in contents of abscisic, jasmonic, salicylic acids and gibberellins in tubers were detected. The data on hormonal status indicated that the enhanced productivity of tms1 transformants was due to auxin and not mediated by other phytohormones. In addition, exogenous cytokinin was shown to upregulate the expression of genes encoding orthologs of auxin receptors. Overall, the results showed that tms1 expression and local increase in IAA level in transformants affect both the balance of endogenous cytokinins and the dynamics of tuberization in response to exogenous hormones (auxin, cytokinin), the latter reaction depending also on the carbohydrate supply. We introduce a basic model for the hormonal network controlling tuberization.

Endogenous levels of cytokinins, indole-3-acetic acid and abscisic acid in in vitro grown potato: A contribution to potato hormonomics

“…The most abundant CK nucleobase in the shoots in our study was iP, while in the roots it was tZ. iP was previously shown to be the most abundant CK nucleobase in potato shoots 32,33 . It has been shown that the biological activity of iP is important for physiological processes in plant shoots 43 .…”

“…There is growing research interest for CK physiology in potato (Solanum tuberosum L.) due to numerous evidence for the involvement of CKs in the commercially important process of tuberisation [18][19][20][21][22][23] . A number of reports containing measurements of phytohormones in various tissues of potato plants grown in various conditions (in vitro, greenhouse) have been published so far 22,[24][25][26][27][28][29][30][31][32][33] . Data on amounts of particular molecular forms of isoprenoid CKs, as well as the auxin indole-3-acetic acid (IAA), and abscisic acid (ABA), measured in control plants in these studies, are summarised in Table 1.…”

“…Among the publications listed in Table 1, only few include reports on endogenous levels of certain CK conjugates 25 or cZ-type CKs 32,33 in potato. The first report on the whole CK profile of potato shoots and roots (cv.…”

Increased arbuscular mycorrhizal fungal colonization reduces yield loss of rice (Oryza sativa L.) under drought

“…ABA and IAA were analyzed at the Plant Physiology Laboratory, Wageningen University, the Netherlands. The extraction and analyses of ABA and IAA were done as described in Kolachevskaya et al (2017) except that the weight of the samples was 4 mg DW.…”

Cytokinin perception in potato: New features of canonic players

“…All StHKs demonstrated high affinity for trans -zeatin, with similar K d at the nanomolar level (Table 3). The determined K d values were close to the values of analogous constants for CK receptors of other species (Lomin et al ., 2012, 2015, Kuderová et al ., 2015) and were well correlated with concentrations of active CKs in planta (Hirose et al ., 2008) including potato (Kolachevskaya et al ., 2017, 2018).…”