Gémes Katalin, Mellidou Ιfigeneia, Karamanoli Katerina, Beris Despoina, Park Ky Young, Matsi Theodora, Haralampidis Kosmas, Constantinidou Helen-Isis, Roubelakis-Angelakis Kalliopi A
Department of Biology, University of Crete, Voutes University Campus, 70013 Heraklion, Greece; Biological Research Centre, Hungarian Academy of Sciences, H-6726 Szeged, Temesvari krt. 62, Hungary.
School of Agriculture, Aristotle University, 54124 Thessaloniki, Greece.
J Plant Physiol. 2017 Apr;211:1-12. doi: 10.1016/j.jplph.2016.12.012. Epub 2017 Jan 15.
Polyamine (PA) homeostasis is associated with plant development, growth and responses to biotic/abiotic stresses. Apoplastic PA oxidase (PAO) catalyzes the oxidation of PAs contributing to cellular homeostasis of reactive oxygen species (ROS) and PAs. In tobacco, PAs decrease with plant age, while apoplastic PAO activity increases. Our previous results with young transgenic tobacco plants with enhanced/reduced apoplastic PAO activity (S-ZmPAO/AS-ZmPAO, respectively) established the importance of apoplastic PAO in controlling tolerance to short-term salt stress. However, it remains unclear if the apoplastic PAO pathway is important for salt tolerance at later stages of plant development. In this work, we examined whether apoplastic PAO controls also plant development and tolerance of adult plants during long-term salt stress. The AS-ZmPAO plants contained higher Ca during salt stress, showing also reduced chlorophyll content index (CCI), leaf area and biomass but taller phenotype compared to the wild-type plants during salt. On the contrary, the S-ZmPAO had more leaves with slightly greater size compared to the AS-ZmPAO and higher antioxidant genes/enzyme activities. Accumulation of proline in the roots was evident at prolonged stress and correlated negatively with PAO deregulation as did the transcripts of genes mediating ethylene biosynthesis. In contrast to the strong effect of apoplastic PAO to salt tolerance in young plants described previously, the effect it exerts at later stages of development is rather moderate. However, the different phenotypes observed in plants deregulating PAO reinforce the view that apoplastic PAO exerts multifaceted roles on plant growth and stress responses. Our data suggest that deregulation of the apoplastic PAO can be further examined as a potential approach to breed plants with enhanced/reduced tolerance to abiotic stress with minimal associated trade-offs.
多胺（PA）稳态与植物发育、生长以及对生物/非生物胁迫的响应相关。质外体PA氧化酶（PAO）催化PA的氧化，有助于活性氧（ROS）和PA的细胞稳态。在烟草中，PA含量随植株年龄增长而降低，而质外体PAO活性增加。我们之前对质外体PAO活性增强/降低的年轻转基因烟草植株（分别为S-ZmPAO/AS-ZmPAO）的研究结果证实了质外体PAO在控制短期盐胁迫耐受性方面的重要性。然而，尚不清楚质外体PAO途径在植物发育后期对耐盐性是否重要。在这项研究中，我们研究了质外体PAO是否也控制成年植株在长期盐胁迫期间的发育和耐受性。在盐胁迫期间，AS-ZmPAO植株的钙含量较高，叶绿素含量指数（CCI）、叶面积和生物量也降低，但与野生型植株相比，盐胁迫期间植株更高。相反，与AS-ZmPAO相比，S-ZmPAO的叶片更多，叶片尺寸略大，抗氧化基因/酶活性更高。在长期胁迫下，脯氨酸在根中的积累明显，并且与PAO失调呈负相关，介导乙烯生物合成的基因转录本也是如此。与之前描述的质外体PAO对年轻植株耐盐性的强烈影响相反，它在发育后期发挥的作用相当温和。然而，在PAO失调的植株中观察到的不同表型强化了这样一种观点，即质外体PAO在植物生长和胁迫响应中发挥多方面作用。我们的数据表明，质外体PAO失调可以作为一种潜在方法进一步研究，以培育对非生物胁迫耐受性增强/降低且相关权衡最小的植物。
