Genome-Wide Identification, Phylogeny, and Expression Analysis of ARF Genes Involved in Vegetative Organs Development in Switchgrass

Functional analysis of ARF1 from Cymbidium goeringii in IAA response during leaf development

Background

Cymbidium is an economically important genus of flowering orchids cultivated in China because of showing graceful leaf shapes and elegant flower coloration. However, the deterioration of the ecological environment and the difficulty of conservation management have become increasing challenges for maintaining its germplasm resources. ARFs are critical transcription factors in the auxin signaling pathway and have been found to play pivotal roles in leaf growth and development in previous studies. However, their functions and mechanisms in Cymbidium goeringii remain to be clarified.

Methods

The sequence of the CgARF1 gene was analyzed by bioinformatics. The expression of this gene in different tissues and under IAA treatment was detected by quantitative real-time PCR analysis. The CgARF1 gene was overexpressed in wild-type Arabidopsis and Nicotiana benthamiana via the Agrobacterium infection method. Acetone-ethanol solvent extraction was applied for the determination of chlorophyll contents, and the contents of endogenous hormones were determined using the enzyme-linked immunosorbent assay technique.

Results

CgARF1 cloned from C. goeringii 'Songmei' was 2,049 bp in length and encoded 682 amino acids containing three typical domains: a B3 DNA binding domain, an Aux_resp domain and an AUX/IXX family domain. The expression pattern of CgARF1 in different tissues of C. goeringii showed that its expression was highest in the leaves and changed greatly under IAA treatment. Subcellular localization studies showed that the protein was mainly localized in the cell nucleus. CgARF1-overexpressing lines exhibited leaf senescence and a decreased chlorophyll content. Under IAA treatment, CgARF1 regulates the rooting length, rooting number and rooting rate from detached leaves. The levels of endogenous hormones in transgenic leaves were also significantly changed.

Conclusion

These results indicated that CgARF1 overexpression is responsive to IAA treatment during leaf development. This study provides a foundation for future research on the function of the ARF gene family in C. goeringii.

Genome-Wide Analysis of the TCP Gene Family in Switchgrass (Panicum virgatum L.)

The plant-specific transcription factor TCPs play multiple roles in plant growth, development, and stress responses. However, a genome-wide analysis of TCP proteins and their roles in salt stress has not been declared in switchgrass (Panicum virgatum L.). In this study, 42 PvTCP genes (PvTCPs) were identified from the switchgrass genome and 38 members can be anchored to its chromosomes unevenly. Nine PvTCPs were predicted to be microRNA319 (miR319) targets. Furthermore, PvTCPs can be divided into three clades according to the phylogeny and conserved domains. Members in the same clade have the similar gene structure and motif localization. Although all PvTCPs were expressed in tested tissues, their expression profiles were different under normal condition. The specific expression may indicate their different roles in plant growth and development. In addition, approximately 20 cis-acting elements were detected in the promoters of PvTCPs, and 40% were related to stress response. Moreover, the expression profiles of PvTCPs under salt stress were also analyzed and 29 PvTCPs were regulated after NaCl treatment. Taken together, the PvTCP gene family was analyzed at a genome-wide level and their possible functions in salt stress, which lay the basis for further functional analysis of PvTCPs in switchgrass.

Genome-Wide Identification and Characterization of the ALOG Domain Genes in Rice

The ALOG domain genes, named after the Arabidopsis LSH1 and Oryza G1 (ALOG) proteins, have frequently been reported as key developmental regulators in rice and Arabidopsis. However, the investigation of the ALOG gene family is limited. Here, we conducted a genome-wide investigation of the ALOG gene family in rice and six other species. In total, eighty-four ALOG domain genes were identified from the seven species, of which fourteen ALOG domain genes (OsG1/G1Ls) were identified in the rice genome. The fourteen OsG1/G1Ls were unevenly distributed on eight chromosomes, and we found that eight segmental duplications contributed to the expansion of OsG1/G1Ls in the rice genome. The eighty-four ALOG family genes from seven species were classified into six clusters, and the ALOG domain-defined motifs 1, 2, and 3 were highly conserved across species according to the phylogenetic and structural analysis. However, the newly identified motifs 4 and 5 were only present in monocots, indicating a specified function in monocots. Moreover, OsG1/G1Ls exhibited tissue-specific expression patterns. Coexpression analysis suggested that OsG1 integrates OsMADS50 and the downstream MADS-box genes, such as OsMADS1, to regulate the development of rice inflorescence; OsG1L7 potentially associates with OsMADS22 and OsMADS55 to regulate stem elongation. In addition, comparative expression analysis revealed the conserved biological functions of ALOG family genes among rice, maize, and Arabidopsis. These results have shed light on the functional study of ALOG family genes in rice and other plants.