Evaluating auxin distribution in tomato (Solanum lycopersicum) through an analysis of the PIN and AUX/LAX gene families

Abstract

SUMMARYThe temporal and spatial control of auxin distribution has a key role in the regulation of plant growth and development, and much has been learnt about the mechanisms that influence auxin pools and gradients in vegetative tissues, particularly in Arabidopsis. For example polar auxin transport, mediated by PIN and AUX/ LAX proteins, is central to the control of auxin distribution. In contrast, very little information is known about the dynamics of auxin distribution and the molecular basis of its transport within and between fruit tissues, despite the fact that auxin regulates many aspects of fruit development, which include fruit formation, expansion, ripening and abscission. In addition, functional information regarding the key regulators of auxin fluxes during both vegetative and reproductive development in species other than Arabidopsis is scarce. To address these issues, we have investigated the spatiotemporal distribution of auxin during tomato (Solanum lycopersicum) fruit development and the function of the PIN and AUX/LAX gene families. Differential concentrations of auxin become apparent during early fruit growth, with auxin levels being higher in internal tissues than in the fruit pericarp and the pattern of auxin accumulation depended on polar transport. Ten tomato PIN (SlPIN1 to 10) and five AUX/LAX (SlLAX1 to 5) genes were identified and found to display heterogeneous expression patterns, with tissue and developmental-stage specificity. RNAi-mediated co-silencing of SlPIN4 and SlPIN3 did not affect fruit development, which suggested functional redundancy of PIN proteins, but did lead to a vegetative phenotype, and revealed a role for these genes in the regulation of tomato shoot architecture.

Comprehensive Tissue-Specific Transcriptome Analysis Reveals Distinct Regulatory Programs during Early Tomato Fruit Development

“…S6F) are consistent with previous reports of increased bioactive GA content and GA20ox transcription after pollination (Serrani et al, 2007(Serrani et al, , 2008de Jong et al, 2011). However, it was not previously known that a GA20ox transcript increases particularly in the funiculus, which is also a site of high auxin activity (Pattison and Catalá, 2012;Fig. 9F).…”

“…6E). This cluster included AUXIN RESPONSE FACTOR3 (ARF3) and ARF19-1, which encode transcription factors involved in auxin signaling (Zouine et al, 2014), and homologs of the Arabidopsis transcription factors PLETHORA, SUPERMAN, and INDEHISCENT, which regulate auxin biosynthesis and activity (Nibau et al, 2011;Kay et al, 2013;Pinon et al, 2013), which is congruent with previous reports of high auxin activity in this tissue (Pattison and Catalá, 2012). This cluster also contained a large number of genes encoding kinases, in particular several members of Leu-rich repeat receptor-like kinase subfamily XI/XII (iTAK database family 1.12.4), such as the Arabidopsis HAESA proteins, which are expressed during abscission zone differentiation (Jinn et al, 2000).…”

“…Common centers of gene expression for auxin biosynthesis and transport genes (Fig. 9D) are consistent with evidence that the seeds are the predominant site of auxin biosynthesis (Mapelli et al, 1978), and the funiculus and placenta represent important transport routes (Pattison and Catalá, 2012). The diverse expression profiles of genes related to auxin signaling (Fig.…”

“…9A). Interestingly, the expression profiles of these genes in the seed and funiculus overlap with maximal auxin activity, as indicated by DR5 reporter expression (Pattison and Catalá 2012), suggesting that they are the main genes involved in auxin synthesis in developing seeds. Common centers of gene expression for auxin biosynthesis and transport genes (Fig.…”

Transcript Profiles of Auxin Efflux Carrier and IAA-Amido Synthetase Genes Suggest the Role of Auxin on Apple (<i>Malus</i> × <i>domestica</i>) Fruit Maturation Patterns

“…The role of auxin in cell division and cell enlargement during fruit development has been well elucidated with auxin treatment studies [13] [33]. Specific distribution of auxin in fruit tissues by the function of auxin transporters has been shown to regulate fruit development and ripening [34]- [39]. However, crosstalk among hormones rather than individual action is most likely to be the common theme regulating most biological processes including fruit ripening [31] [32] [40]- [42].…”