A Sheathed Spike Gene, TaWUS-like Inhibits Stem Elongation in Common Wheat by Regulating Hormone Levels

Background: The elongation and development of wheat (Triticum aestivum L.) stem play an important role in plant architecture. Shortened stem would result in sheathed spike and low yield in crops. To elucidate the molecular mechanisms underlying sheathed spike would be helpful for plant architecture and yield. Results: We found a novel gene, TaWUS-like（WUSCHEL-related homeobox like）, which regulated sheathed spike and plant architecture in wheat. The plant height of overexpression transgenic lines were significantly decreased and the spike was not completely elongated and enclosed in flag leaf sheaths. Besides, the increase of tiller angle resulted in loose plant architecture and lower yield. The statistical and cytological analysis demonstrated that the length of the uppermost and secondary internode was significantly shortened, especially the uppermost internode was only half length of wild-type. The parenchyma cells obviously reduced and elongated insufficiently. The analysis of hormone content showed that there was a lack of GA3 in internodes but a higher BR content. Conclusions: TaWUS-like may inhibit the synthesis of GA and/or BR and affect the function of signal transduction of these hormones, which further caused stem shortening and plant dwarfing in wheat.

Identification of Candidate Gene for Internode Length in Rice to Enhance Resistance to Lodging Using QTL Analysis

Internode length and stem diameter are the primary traits affecting the lodging resistance of rice. Traits related to the length of the panicle (LP), uppermost internode (LUI), second internode (LSI), third internode (LTI), fourth internode (LFI), lowest internode (LLI) as well as stem diameter at the uppermost internode (SDUI), second internode (SDSI), third internode (SDTI), fourth internode (SDFI), and lowest internode (SDLI) in 120 Cheongcheong/Nagdong doubled haploid population were investigated using a quantitative trait locus (QTL) analysis. Thirty-four QTL regions affected LP and the length of each internode. Twenty-six QTL regions were associated with the stem diameter of each internode. RM12285-RM212 on chromosome 1 contained 10 QTLs related to the internode length, which have overlapped for over 2 years. Twenty-three candidate genes were screened using mark interval. Among the candidate genes, Os01g0803900, named OsCYPq1, which is in the Cytochrome P450 family, might be involved in gibberellins (GA) synthesis. GA is an essential plant growth regulator that affects plant height. OsCYPq1 catalyzes oxidation steps in the middle part of the GA pathway. OsCYPq1 is expected to provide valuable information to improve the marker assessment for target traits and QTL gene cloning in rice.

Genome-wide association analysis of panicle exsertion and uppermost internode in rice (Oryza sativa L.)

Background Rice (Oryza sativa L.) yield is seriously influenced by panicle exsertion (PE) and the uppermost internode (UI) through panicle enclosure or energy transport during grain-filling stages. We evaluated the traits of PE and UI of 205 rice accessions in two independent environments and performed genome-wide association (GWAS) to explore the key genes controlling PE and UI, which could be used to improve panicle enclosure in rice breeding. Results In this study, extensive genetic variation was found in both PE and UI among the 205 rice accessions, and 10.7% of accessions had panicle enclosure (PE/UI ≤ 0). Correlation analysis revealed that PE was significantly positively correlated with 1000-grain weight (1000-GW) but negatively correlated with heading date (HD), and UI was significantly positively correlated with HD but no significantly correlated with 1000-GW. A total of 22 and 24 quantitative trait loci (QTLs) were identified for PE and UI using GWAS, respectively. Eight loci for PE and nine loci for UI were simultaneously detected both in 2015 and in 2016, seven loci had adjacent physical positions between PE and UI, and ten loci for PE and seven loci for UI were located in previously reported QTLs. Further, we identified the CYP734A4 gene, encoding a cytochrome P450 monooxygenase, and the OsLIS-L1 gene, encoding a lissencephaly type-1-like protein, as causal genes for qPE14 and qUI14, and for qPE19, respectively. PE and UI were both significantly shorter in these two genes’ mutants than in WT. Allelic Hap.1/2/4 of CYP734A4 and Hap.1/2/4 of OsLIS-L1 increased PE, UI, PE/UI, and 1000-GW, but Hap.3 of CYP734A4 and Hap.3 of OsLIS-L1 reduced them. In addition, six candidate genes were also detected for four key novel loci, qPE16, qPE21, qUI1, and qUI18, that seemed to be related to PE and UI. Conclusions Our results provide new information on the genetic architecture of PE and UI in rice, confirming that the CYP734A4 and OsLIS-L1 genes participate in PE and UI regulation, which could improve our understanding of the regulatory mechanism of PE and UI for rice breeding in the future.