Ectopic expression of the Coffea canephora SERK1 homolog‐induced differential transcription of genes involved in auxin metabolism and in the developmental control of embryogenesis

Abstract

Somatic embryogenesis receptor-like kinase 1 (SERK1) is a membrane receptor that might serve as common co-regulator of plant cell differentiation processes by forming heterodimers with specific receptor-like kinases. The Coffea canephora SERK1 homolog (CcSERK1) was cloned in this work, and its early function in the transcription of embryogenesis master genes and of genes encoding proteins involved in auxin metabolism was investigated by externally manipulating its expression in embryogenic leaf explants, before the appearance of embryogenic structures. Overexpression of CcSERK1 early during embryogenesis caused an increase in the number of somatic embryos when the 55-day process was completed. Suppression of CcSERK1 expression by RNA interference almost abolished somatic embryogenesis. Real time-PCR experiments revealed that the transcription of the CcAGL15, CcWUS, CcBBM, CcPKL, CcYUC1, CcPIN1 and CcPIN4 homologs was modified in direct proportion to the expression of CcSERK1 and that only CcLEC1 was inversely affected by the expression levels of CcSERK1. The expression of the CcYUC4 homolog was induced to more than 80-fold under CcSERK1 overexpression conditions, but it was also induced when CcSERK1 expression was silenced. The level of CcTIR1 was not affected by CcSERK1 overexpression but was almost abolished during CcSERK1 silencing. These results suggest that CcSERK1 co-regulates the induction of somatic embryogenesis in Coffea canephora by early activation of YUC-dependent auxin biosynthesis, auxin transport mediated by PIN1 and PIN4, and probably auxin perception by the TIR1 receptor, leading to the induction of early-stage homeotic genes (CcAGL15, CcWUS, CcPKL and CcBBM) and repression of late-stage homeotic genes (CcLec1).

Using Morphogenic Genes to Improve Recovery and Regeneration of Transgenic Plants

“…Similar to observations in which overexpression of genes involved in meristem initiation and maintenance have increased a pre-existing embryogenic response [19,20,21,22,24,25,26], their ectopic overexpression has also been reported to stimulate the formation of somatic embryos where they would otherwise not be observed.…”

“…This demonstrated that SERK1 stimulated an enhanced somatic embryo response from germinating seedlings placed on media capable of eliciting this response already. Similarly, overexpression of the Coffea canephora SERK1 gene during the in vitro somatic embryogenesis process enhanced the production of somatic embryos by 2-fold, while silencing the gene dramatically reduced the somatic embryogenesis response [19]. Similar conclusions have been reached in reports in which the AGAMOUS-LIKE15 ( AGL15 ) gene was overexpressed, enhancing the formation of secondary somatic embryos from cultured zygotic embryos in Arabidopsis [20], increasing the number of somatic embryos in soybean cultures [21], and again enhancing production of embryogenic callus in cotton [22].…”

Advances and Perspectives in Tissue Culture and Genetic Engineering of Cannabis

“…In the first class, the overexpression of genes leads to an increase in embryogenesis under in vitro conditions in which the formation of somatic embryos is already observed. For instance, overexpression of SOMATIC EMBRYOGENESIS RECEPTOR KINASE1 (SERK1) using CaMV 35S promoter resulted in ~4-fold and 2-fold increases in somatic embryogenesis of Arabidopsis thaliana [ 187 ] and Coffea canephora [ 188 ], respectively. Similarly, further studies in Arabidopsis [ 189 ], cotton [ 190 ], and soybean [ 191 ] have shown an increase in somatic embryogenesis with overexpression of the AGAMOUS-LIKE15 (AGL15) gene, a member of the SERK1 protein complex [ 192 ].…”

Signaling Overview of Plant Somatic Embryogenesis

“…Some of these TFs are shared among a variety of plant species (Supplementary Table S1). Among the TFs that have been found during the induction of SE in different species are ABAINSENSITIVE 3 (ABI3) (Shiota et al, 1998), AGAMOUS LIKE (AGL) (Harding et al, 2003; Thakare et al, 2008; Zhai et al, 2016), BABY BOOM (BBM) (Florez et al, 2015), CUP SHAPED COTYLEDONS (CUC), FUSCA3 (FUS3) (Luerûen et al, 1998), LEAFY COTYLEDON (LEC) (Iwase et al, 2015) , LEAFY COTYLEDON LIKE (LIL) (Kwong et al, 2003), SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE1 (SERK1) (Pérez-Pascual et al, 2018) , RWP-RK DOMAIN-CONTAINING 4 (RKD4)/GROUNDED (GRD) (Waki et al, 2011). VIVIPAROUS1 (VP1) (Footitt et al, 2003), and WUSCHEL (WUS) (Arroyo-Herrera et al, 2008; Xiao et al, 2018).…”