Conservation and Diversification of the SHR-SCR-SCL23 Regulatory Network in the Development of the Functional Endodermis in Arabidopsis Shoots

Abstract

Development of the functional endodermis of Arabidopsis thaliana roots is controlled, in part, by GRAS transcription factors, namely SHORT-ROOT (SHR), SCARECROW (SCR), and SCARECROW-LIKE 23 (SCL23). Recently, it has been shown that the SHR-SCR-SCL23 regulatory module is also essential for specification of the endodermis (known as the bundle sheath) in leaves. Nevertheless, compared with what is known about the role of the SHR-SCR-SCL23 regulatory network in roots, the molecular interactions of SHR, SCR, and SCL23 are much less understood in shoots. Here, we show that SHR forms protein complexes with SCL23 to regulate transcription of SCL23 in shoots, similar to the regulation mode of SCR expression. Our results indicate that SHR acts as master regulator to directly activate the expression of SCR and SCL23. In the SHR-SCR-SCL23 network, we found a previously uncharacterized negative feedback loop whereby SCL23 modulates SHR levels. Through molecular, genetic, physiological, and morphological analyses, we also reveal that the SHR-SCR-SCL23 module plays a key role in the formation of the endodermis (known as the starch sheath) in hypocotyls. Taken together, our results provide new insights into the regulatory role of the SHR-SCR-SCL23 network in the endodermis development in both roots and shoots.

Genome-wide survey and expression analyses of the GRAS gene family in Brassica napus reveals their roles in root development and stress response

“…The SAW motif comprised four sub-motifs: RVER, W-G, L-W, and SAW ( Fig. 2 and SL subcellular localization, PI isoelectric point, MW molecular weight, aa amino acid S2), consistent with the previous results (Yoon et al 2016). We further identified 24 conserved motifs outside the GRAS domain at the N-terminal of the GRAS proteins in A. thaliana, B. rapa, B. oleracea, and B. napus using the MEME website.…”

Transcriptome dynamics in developing leaves from C3and C4Flaveriaspecies reveal determinants of Kranz anatomy

“…Bundle sheath tissue in leaves is equivalent to the root endodermis and the starch sheath of hypocotyls and the development of bundle sheath cells is at least partially conserved to root endodermis development and differentiation (Kyung Yoon et al, 2016; Wysocka-Diller et al, 2000; Lim et al, 2005; Slewinski, 2013; Cui et al, 2014). It is known that the interplay of the GRAS-type transcription factors SCARECROW (SCR) and SHORT-ROOT (SHR) is essential to specify the root endodermis identity as well as for the correct bundle sheath development in the C 3 species Arabidopsis and the C 4 species maize (Slewinski et al, 2012; Cui et al, 2014; Slewinski et al, 2014).…”

Cloning and Characterization of ThSHRs and ThSCR Transcription Factors in Taxodium Hybrid ‘Zhongshanshan 406’

“…Transcription factors (TFs), also known as trans-acting factors, are located in the nuclei and exhibit a special interaction with cis-regulatory elements in the gene promoter regions. As a result, expression of a set of downstream functionally-related target genes are regulated in a spatio-temporal specific manner [ 33 ]. Hence, TFs are core components of gene regulation networks [ 33 , 34 ].…”

“…As a result, expression of a set of downstream functionally-related target genes are regulated in a spatio-temporal specific manner [ 33 ]. Hence, TFs are core components of gene regulation networks [ 33 , 34 ]. SHR and SCR belong to the plant-specific GRAS TF family [ 32 , 35 , 36 ].…”

“…They are essential to regulate the asymmetric cell divisions, and thereby to generate the root ground tissue [ 38 , 39 , 40 ]. To date, a number of SHR and SCR genes involved in seedling root system have been studied systematically [ 9 , 12 , 33 ]. However, studies in SHR and SCR genes involving adventitious roots were few and far between.…”