Transformation of miniature potted rose (Rosa hybrida cv. Linda) with P SAG12 -ipt gene delays leaf senescence and enhances resistance to exogenous ethylene

Abstract

KEY MESSAGE : The P ( SAG12 ) -ipt gene was transferred to miniature rose, as the first woody species, resulting in increased ethylene resistance due to specific up-regulation of the ipt gene under senescence promoting conditions. Transgenic plants of Rosa hybrida 'Linda' were obtained via transformation with Agrobacterium tumefaciens strain harboring the binary vector pSG529(+) containing the P( SAG12 )-ipt construct. A. tumefaciens strains AGL1, GV3850 and LBA4404 (containing P(35S)-INTGUS gene) were used for transformation of embryogenic callus, but transgenic shoots were obtained only when AGL1 was applied. The highest transformation frequency was 10 % and it was achieved when half MS medium was used for the dilution of overnight culture of Agrobacterium. Southern blot confirmed integration of 1-6 copies of the nptII gene into the rose genome in the tested lines. Four transgenic lines were obtained which were morphologically true-to-type and indistinguishable from Wt shoots while they were in in vitro cultures. Adventitious root induction was more difficult in transgenic shoots compared to the Wt shoots, however, one of the transgenic lines (line 6) was rooted and subsequently analyzed phenotypically. The ipt expression levels were determined in this line after exposure to exogenous ethylene (3.5 μl l(-1)) and/or darkness. Darkness resulted in twofold up-regulation of ipt expression, whereas darkness combined with ethylene caused eightfold up-regulation in line 6 compared to Wt plants. The transgenic line had significantly higher content of chlorophyll at the end of the treatment period compared to Wt plants.

Senescence is delayed when ramie (Boehmeria nivea L.) is transformed with the isopentyl transferase (ipt) gene under control of the SAG12 promoter

“…Our data showed that transformation of ramie with the P SAG12 ‐ ipt gene delayed leaf senescence and enhanced biomass. Roses and stay‐green lines have been obtained with similar features to those described in the present paper for ramie 29. Because of the worldwide economic importance of ramie, the decreased senescence observed in transgenic P SAG12 ‐ ipt ramie has commercial value.…”

“…Ethylene is known to promote the leaf senescence process 29. To confirm that leaf senescence was delayed in ipt ‐overexpressing plants, an ethephon‐induced leaf senescence test was conducted using the above two ipt ‐overexpressing plants (T19 and T20) and WT plants.…”

Ethylene Role in Plant Growth, Development and Senescence: Interaction with Other Phytohormones

“…The construct SAG12::IPT gene has been studied in different species and all showed delayed senescence. This strategy was effective in delaying leaf senescence in several crops such as alfalfa ( Medicago sativa ; Calderini et al, 2007), broccoli ( Brassica oleracea ; Chen et al, 2001), cassava ( Manihot esculenta ; Zhang et al, 2010), creeping bentgrass ( Agrostis stolonifera ; Xu et al, 2009), lettuce (McCabe et al, 2001), petunia (Chang et al, 2003), rose ( Rosa hybrid ; Zakizadeh et al, 2013), tobacco (Jordi et al, 2000), and wheat ( Triticum aestivum ; Sýkorová, 2008). The senescence delay reduced ethylene biosynthesis in the transformed plants.…”

“…The overproduction of cytokinins in petunia flowers transformed with P -S AG12- IPT has been reported to delay corolla senescence and decrease sensitivity to ethylene (Chang et al, 2003). The PSAG12-IPT gene was also transferred to a miniature rose, as the first woody species to be transformed with SAG12-IPT system, resulting in increased ethylene tolerance due to specific up-regulation of the IPT gene under senescence promoting conditions (Zakizadeh et al, 2013). An increase in ethylene, in petunia flowers exogenously treated with cytokinin, was found during senescence, and the lack of a negative effect can be explained considering the expression of the ethylene receptors was down-regulated by treatment with BA (Trivellini et al, 2015).…”

Transgenics in Ornamental Crops:Creating Novelties in Economically Important Cut Flowers

“…Specific upregulation of ipt gene under conditions favouring senescence in roses transformed with fusion gene, PSAG12-ipt resulted in better post-harvest life as transgenic plants showed resistance to early leaf senescence and ethylene production 28 . Progressing towards the advancement in transgenic breeding, several novel technologies like nextgeneration sequencing methods (NGS), parallel detection of SNPs via chip technologies, targeted mutagenesis via designer nucleases and related methods have boosted research in many model as well as non-model plants 19 , and have also provided possible avenues for advancement in rose breeding.…”