Deregulation of the OsmiR160 Target Gene OsARF18 Causes Growth and Developmental Defects with an Alteration of Auxin Signaling in Rice

Abstract

MicroRNAs (miRNAs) control gene expression as key negative regulators at the post-transcriptional level. MiR160 plays a pivotal role in Arabidopsis growth and development through repressing expression of its target AUXIN RESPONSE FACTOR (ARF) genes; however, the function of miR160 in monocots remains elusive. In this study, we found that the mature rice miR160 (OsmiR160) was mainly derived from OsMIR160a and OsMIR160b genes. Among four potential OsmiR160 target OsARF genes, the OsARF18 transcript was cleaved at the OsmiR160 target site. Rice transgenic plants (named mOsARF18) expressing an OsmiR160-resistant version of OsARF18 exhibited pleiotropic defects in growth and development, including dwarf stature, rolled leaves, and small seeds. mOsARF18 leaves were abnormal in bulliform cell differentiation and epidermal cell division. Starch accumulation in mOsARF18 seeds was also reduced. Moreover, auxin induced expression of OsMIR160a, OsMIR160b, and OsARF18, whereas expression of OsMIR160a and OsMIR160b as well as genes involved in auxin signaling was altered in mOsARF18 plants. Our results show that negative regulation of OsARF18 expression by OsmiR160 is critical for rice growth and development via affecting auxin signaling, which will advance future studies on the molecular mechanism by which miR160 fine-tunes auxin signaling in plants.

Evidence that auxin is required for normal seed size and starch synthesis in pea

“…A positive regulatory role for auxin in starch synthesis in rice was suggested by Abu‐Zaitoon et al . (), who reported concurrent increases in auxin and starch concentrations during rice grain development; furthermore, IAA application was reported to increase the starch content of rice grains (Javid et al ., ), and studies on a rice auxin response factor, OSARF18, also indicate a positive role for auxin signalling in starch synthesis (Huang et al ., ). In cultured tobacco cells, exogenous auxin downregulated starch‐related genes (Miyazawa et al ., ), whereas by contrast, a repressor of auxin action, SlARF4, downregulated AGPase gene expression in tomato fruits (Sagar et al ., ), consistent with our findings.…”

Genome-Wide Identification and Expression Analysis of Auxin Response Factor (ARF) Gene Family in Longan (Dimocarpus longan L.)

“…In Arabidopsis, ARF2 regulates leaf senescence and floral organ abscission independently of the ethylene and cytokinin response pathways [20]; ARF6, NPH4/ARF7, and ARF8 affect leaf and inflorescence growth, promoting hypocotyl elongation [21,22]. In rice, negative regulation of OsARF18 expression by OsmiR160 is critical for rice normal growth and development [23]; OsARF12 is regarded as one of major player in phosphate-induced auxin responses, indicating that ARFs might be involved in phosphate homeostasis in crops [24]. In tomato, SlARF7 acts as a negative regulator of fruit set after pollination and fertilization, and moderates auxin response during fruit growth [25]; SlARF4 controls chlorophyll accumulation in fruit and down-regulation of SlARF4 results in a dark-green immature fruit phenotype with increased chloroplasts [26].…”

Dynamic roles of microRNAs in nutrient acquisition and plant adaptation under nutrient stress: A review

“…Among all the studied hormones in conjunction with miRNAs based responses for nutrient stress, auxin and cytokinins are the two most prominent groups of hormones involved in this mechanism. Several miRNAs are involved in hormones mediated responses, such as miR160 affect later roots formation via auxin signaling pathway thereby targeting auxin responsive factor (ARF18) in rice (Huang et al, 2016). Further, miR847 and miR390 controls lateral root development in Arabidopsis and it was regulated via auxin-dependent pathway (Yoon et al, 2010;Wang and Guo, 2015).…”