Robust increase of leaf size by Arabidopsis thaliana GRF3-like transcription factors under different growth conditions

Abstract

An increase in crop yield is essential to reassure food security to meet the accelerating global demand. Several genetic modifications can increase organ size, which in turn might boost crop yield. Still, only in a few cases their performance has been evaluated under stress conditions. MicroRNA miR396 repress the expression of GROWTH-REGULATING FACTOR (GRF) genes that codes for transcription factors that promote organ growth. Here, we show that both Arabidopsis thaliana At-GRF2 and At-GRF3 genes resistant to miR396 activity (rGRF2 and rGRF3) increased organ size, but only rGRF3 can produce this effect without causing morphological defects. Furthermore, introduction of At-rGRF3 in Brassica oleracea can increase organ size, and when At-rGRF3 homologs from soybean and rice are introduced in Arabidopsis, leaf size is also increased. This suggests that regulation of GRF3 activity by miR396 is important for organ growth in a broad range of species. Plants harboring rGRF3 have larger leaves also under drought stress, a condition that stimulates miR396 accumulation. These plants also showed an increase in the resistance to virulent bacteria, suggesting that the size increment promoted by rGRF3 occurs without an obvious cost on plant defenses. Our findings indicate that rGRF3 can increase plant organ size under both normal and stress conditions and is a valuable tool for biotechnological applications.

Differential Expression of Maize and Teosinte microRNAs under Submergence, Drought, and Alternated Stress

“…The growth and development processes are driven by hormonal signaling pathways that are fundamental in the response to submergence and drought in plants [ 41 ], where transcription factors and miRNAs participate. Several differentially expressed miRNAs identified in this work are known to act over target genes encoding transcription factors such as miR156 (squamosa promoter-binding protein like, SPL) [ 42 , 43 , 44 ], miR159 (giberellic acid-MYB transcription factor, GAMYB [ 28 , 29 ]), miR164 (NAM-ATAF-CUC domain transcription factor NAC, MYB [ 45 ]), miR166 (basic leucine zipper transcription factor, HD-ZIP III [ 46 , 47 ]), miR167 (auxin-responsive factor, ARF [ 30 , 35 , 48 ]), miR169 (nuclear transcription factor Y subunit alpha, NFYA [ 49 , 50 , 51 , 52 ]), miR319 (teosinte branched1/cycloidea/proliferating cell nuclear antigen factor, TCP [ 53 ]), and miR396 (growth-regulating factor, GRF [ 54 , 55 ]). Other target genes predicted in this study are listed in Table S6 .…”

Biological roles and an evolutionary sketch of the GRF-GIF transcriptional complex in plants

“…The contradiction may be comprehensible in light of an additional function of AtGRFs in the root: ectopic AtGRF expression interferes with the normal patterning of cell divisions in the stem cell niche and organization of the quiescent center (QC). Nevertheless, it is intriguing that the heterologous overexpression of At-rGRF3 in B. oleracea resulted in longer roots than the wild type (63).…”

Conserved miR396b-GRF Regulation Is Involved in Abiotic Stress Responses in Pitaya (Hylocereus polyrhizus)

“…Liu et al found that transgenic miR396 -overexpressing plants are more tolerant to drought than wild-type plants in Arabidopsis [53]. In particular, the AtGRF3 transgene yielded an increase in leaf size under mild drought stress and showed enhanced resistance to certain plant pathogens [54]. Further analysis revealed that Sp-miR396a-5p transcription levels are up-regulated under salt and drought stresses, and additionally, the expression of Sp-miR396a-5p is down-regulated under pathogen-related biotic stress [55], and the relevant link between salt and alkali stress of osa-miR396c in rice was established by Gao et al [56].…”