Tuning of SlARF10A dosage by sly‐miR160a is critical for auxin‐mediated compound leaf and flower development

Abstract

miR160 adjusts auxin-mediated development by post-transcriptional regulation of the auxin response factors ARF10/16/17. In tomato, knockdown of miR160 (sly-miR160) suggested that it is required for auxin-driven leaf blade outgrowth, but whether additional developmental events are adjusted by sly-miR160 is not clear. Here, the SlMIR160 genes and the genes of its SlARFs targets were edited by CRISPR/Cas9 resulting in the isolation of loss-of-function mutants. In addition, hypomorphic mutants that accumulate variable reduced levels of sly-miR160a were isolated. We found that the loss-of-function mutants in SlMIR160a (CR-slmir160a-6/7) produced only four wiry leaves, whereas the hypomorphic mutants developed leaves and flowers with graded developmental abnormalities. Phenotypic severity correlated with the upregulation of SlARF10A. Consistent with that, double mutants in SlMIR160a and SlARF10A restored leaf and flower development indicating that over-accumulation of SlARF10A underlay the developmental abnormalities exhibited in the CR-slmir160a mutants. Phenotype severity also correlated with the upregulation of the SHOOT MERISTEMLESS homolog Tomato Knotted 2, which in turn activated the transcription of the cytokinin biosynthesis genes SlIPT2 and SlIPT4. However, no change in Tomato Knotted 2 was detected in the absence of SlARF10A, suggesting that it is upregulated due to auxin signaling suppression by SlARF10A. Knockout of sly-miR160a-targeted SlARFs showed that whereas SlARF10A is indispensable for leaf blade outgrowth and floral organ patterning, the functions of SlARF16A and SlARF17 are redundant. Taken together our results suggest that sly-miR160a promotes blade outgrowth as well as leaf and leaflet initiation and floral organ development through the quantitative regulation of its major target SlARF10A.

MicroRNA160 regulates leaf curvature in potato (Solanum tuberosum L. cv. Désirée)

“…ARF10 was also suggested to be the major target in tomato. 33 Even though we could detect miR160-targeted cleavage products of StARF16 through RLM-RACE technique, the expression of StARF16 was not complementary to that of miR160 in our transgenic plants. This atypical miR160-ARF16 expression pattern was also reported in tomato 15 suggesting a complex regulation of ARF16 expression by factors other than miR160.…”

“…It is proposed that different expression levels of C-ARFs results in variable degree of leaf complexity in tomato. 33 Hence, the leaf compounding phenotypes of our potato plants could be attributed to the extent of miR160 overexpression or knockdown.…”

GhARF16‐1 modulates leaf development by transcriptionally regulating the GhKNOX2‐1 gene in cotton

“…In addition, overexpression of miR160 gene under a constitutive CaMV‐35S promoter in tomato resulted in an entire leaflet blade phenotype compared to the wild‐type leaves. Meanwhile the expression level of the tomato Knotted 2 protein (Tkn2) was negatively correlated with miR160 levels and positively correlated with ARF gene expression levels, such as ARF16 (Damodharan et al ., 2018). Consistently, in our study, expression of a miR160‐resistant GhARF16 gene in Arabidopsis and cotton led to significantly increased GhKNOX2‐1 transcripts and deeply serrated leaf margins.…”

The Critical Role of miRNAs in Regulation of Flowering Time and Flower Development

“…Hormone signaling pathways play an essential role in coordinating multiple developmental programs including the germination process, organ morphogenesis, and floral transition in response to various environmental conditions [62]. The latest studies demonstrated that some miRNAs act as a key regulator of auxin signaling pathway and directly or indirectly affect floral transition in different plant species [63][64][65]. Similarly, miR390 and miR393 are involved in controlling the auxin signaling pathway to influence such actions of plants [66][67][68].…”