Genetic dissection of Rhizobium‐induced infection and nodule organogenesis in pea based on ENOD12A and ENOD5 expression analysis

Abstract

In legumes, perception of rhizobial lipochitooligosacharide-based molecules (Nod factors) and subsequent signal transduction triggers transcription of plant symbiosis-specific genes (early nodulins). We present genetic dissection of Nod factor-controlled processes in Pisum sativum using two early nodulin genes PsENOD12a and PsENOD5, that are differentially up-regulated during symbiosis. A novel set of non-nodulating pea mutants in fourteen loci was examined, among which seven loci are not described in Lotus japonicus and Medicago truncatula. Mutants defective in Pssym10, Pssym8, Pssym19, Pssym9 and Pssym7 exhibited no PsENOD12a and PsENOD5 activation in response to Nod factor-producing rhizobia. Thus, a conserved signalling module from the LysM receptor kinase encoded by Pssym10 down to the GRAS transcription factor encoded by Pssym7 is essential for Nod factor-induced gene expression. Of the two investigated genes, PsENOD5 was more strictly regulated; not only requiring the SYM10-SYM7 module, but also SYM35 (NIN transcription factor), SYM14, SYM16 and SYM34. Since Pssym35, Pssym14, Pssym34 and Pssym16 mutants show arrested infection and nodule formation at various stages, PsENOD5 expression seems to be essential for later symbiotic events, when rhizobia enter into plant tissues. Activation of PsENOD12a only requires components involved in early steps of signalling and can be considered as a marker of early symbiotic events preceding infection.

Reproducible hairy root transformation and spot-inoculation methods to study root symbioses of pea

“…It has a large genome (about 4 × 10 9 base pairs [1]) still to be sequenced, and many molecular techniques, especially those of transformation, are difficult to use [1] to study the function of the genes involved in the nodulation process. Yet, the agricultural and economic importance of pea is significant, especially in Canada, so despite the difficulty in manipulating this species, it is relevant to study its beneficial root symbioses and to capitalize on its large collection of symbiotic mutants [2]. Pea production is expected to increase further as farming practises are focusing on agricultural sustainability, with farmers once again utilizing the benefits of crop rotation to decrease fertilizer applications.…”

“…Likely because of the difficulty encountered in pea transformation, there has been only one report of successful nodule formation on composite wild-type/transgenic pea plants [18], and gene complementation in pea mutants deficient in nodulation (i.e., Nod - mutants) has not been previously reported. This has forced researchers studying pea to resort to the transformation of pea genes into close relatives, such as Trifolium repens (white clover) [19] or barrel medic [2,20]. …”

Plant Genetic Control over Infection Thread Development during Legume-Rhizobium Symbiosis

“…However, the molecular products encoding by these loci have not been identified for a long time. The significant progress in identification of genes, controlling IT development, was achieved using two model legumes: M. truncatula and L. japonicus, and it is allowed to identify the sequences of some previously revealed loci in pea [6,[38][39][40].…”

“…The LjNSP2 gene was shown to be suppressed in mature nodules [65]. PsSym7 is an ortholog of the MtNSP2 gene [39,64] and Pssym34 is an ortholog of the MtNSP1 gene [67]. It has been shown that MtNSP1 and MtNSP2 form a complex that is associated with the promoters of the early nodulin genes (in particular, the MtENOD11 gene).…”

Fine localization of the sym31 locus in pea linkage group III

“…В результате за прошедшее десятилетие с использованием анализа геномной синтении были выявлены серии ортологичных симбиотических генов у ряда бобовых культур (Kouchi et al, 2010). У гороха посевного были определены нуклеотидные последовательности симбиотических ге-нов sym7 (Dolgikh et al, 2011), sym8 (Edwards et al, 2007), sym9 (Lévy et al, 2004), sym10 (Zhukov et al, 2008), sym19 (Endre et al, 2002), sym28 (Krusell et al, 2011), sym29 (Krussel et al, 2002), sym33 (Ovchinnikova et al, 2011), sym35 (Borisov et al, 2003) и sym37 (Zhukov et al, 2008). Тем не менее, у гороха не всегда оказывается возможным клонировать ген по гомологии с модельными бобовыми, т.к.…”