Altered expression of polyamine transporters reveals a role for spermidine in the timing of flowering and other developmental response pathways

Abstract

Changes in the levels of polyamines are correlated with the activation or repression of developmental response pathways, but the role of polyamine transporters in the regulation of polyamine homeostasis and thus indirectly gene expression, has not been previously addressed. Here we show that the A. thaliana and rice transporters AtPUT5 and OsPUT1 were localized to the ER, while the AtPUT2, AtPUT3, and OsPUT3 were localized to the chloroplast by transient expression in N. benthamiana. A. thaliana plants that were transformed with OsPUT1 under the control the PUT5 promoter were delayed in flowering by 16days. In contrast, put5 mutants flowered four days earlier than WT plants. The delay of flowering was associated with significantly higher levels of spermidine and spermidine conjugates in the leaves prior to flowering. A similar delay in flowering was also noted in transgenic lines with constitutive expression of either OsPUT1 or OsPUT3. All three transgenic lines had larger rosette leaves, thicker flowering stems, and produced more siliques than wild type plants. In contrast, put5 plants had smaller leaves, thinner flowering stems, and produced fewer siliques. Constitutive expression of PUTs was also associated with an extreme delay in both plant senescence and maturation rate of siliques. These experiments provide the first genetic evidence of polyamine transport in the timing of flowering, and indicate the importance of polyamine transporters in the regulation of flowering and senescence pathways.

The Arabidopsis L-Type Amino Acid Transporter 5 (LAT5/PUT5) Is Expressed in the Phloem and Alters Seed Nitrogen Content When Knocked Out

“…Homozygous lat5-1 mutant plants showed reduced leaf size under normal growth conditions on the soil. This phenotype for the lat5-1 was also reported by Ahmed et al, where they used the same T-DNA insertion line (Salk_007135), but called it as put5 [18]. While the average number of leaves per plant in the lat5-1 did not differ from the WT, the width of rosette leaves, the diameter of leaf protoplast,…”

“…However, the Arabidopsis LATs have been demonstrated to have roles in mediating the transport of a range of substrates including amino acid, polyamine, paraquat, and thiamine [11][12][13][14][15][16][17]. The LAT5 was previously studied for its role in developmental responses, such as flowering and senescence, where it was called PUT5 under the assumption that it is a polyamine uptake transporter [18]. While studies have yet to demonstrate its role in polyamine transport, one report mentioned that PUT5, when expressed in a mutant yeast strain deficient in spermidine transport, increased the sensitivity of the yeast cells to exogenous polyamines and paraquat, suggesting that PUT5 mediates polyamine transport [17].…”

Genome-Wide Identification of Seven Polyamine Oxidase Genes in Camellia sinensis (L.) and Their Expression Patterns Under Various Abiotic Stresses

“…PAs have many important functions in plants. They play a vital role in flowering and development (Ahmed et al, 2017), leaf development and senescence (Sobieszczuk-Nowicka et al, 2015;Sobieszczuk-Nowicka, 2017), and fruit development and maturity (Liu and Moriguchi, 2007;Fortes and Agudelo-Romero, 2018). In addition, PAs are key components of plant abiotic stress responses (Liu et al, 2015;Montilla-Bascon et al, 2017), and their response mechanisms include participation in protein regulation (Sayas et al, 2019), regulation of chemical penetration and photoprotection of chloroplasts (Ioannidis et al, 2016), and control of N/C balance in plants (Moschou et al, 2012).…”

Ectopic expression of GhSAMDC1 improved plant vegetative growth and early flowering through conversion of spermidine to spermine in tobacco

“…www.nature.com/scientificreports/ temperature and oxidative stress [24][25][26][27][28] . Changes in polyamine transporters reveal a significant role of spermidine in the timing of flowering 12 .…”

“…Expression analyses of these genes have been used to evaluate flowering. Many studies have shown that exogenous polyamines and polyamine synthesis inhibitors affect flower bud differentiation and development 12,31,32 .…”