Abstraet t-lomozygous doubled-haploid plantlets derived from anther eulture of wheat {Triticum aestivum L.) and triticale (X Tritieoseeale Wittmack) nre usetui breeding materials. However, effieiency of androgenesis needs improvement. We used media (basic components are the same as 85Df2) each eontaining one of the seven auxins [2,4,5-triehlorophenoxyacetie acid (2,4,5-T), f-chloroptienoxyaeetic acid (pGPA), 3,6-dichtoro-o-anisic aeid (dicamba), 4-aiiiino-3,5,6-trichloropicolinic acid (picloram), indolc-3-hutrytie acid (tBA), iiido!e-3-acetie aeid (lAA), and 2,4-dichtorophenoxyacetie aeid (2,4-D) as a control] m combination with 6-furfurylaminopurine (kinetin). In addition, each of the four cytokinins [6-benzylaininopurine (6-BA), 2-isopentylnyt adenine (2-ip), 6-(4-hydroxy-3-methytbiit-2-enylamino) purine (zeatin), and kinetin as a control] was tested in eombination with t-naphthatene acetic acid (NAA). Anthers containing microspores at inid-uninucteate stage from five wheat cuttivars (Angus, Genturk, Ghris, Kitt, and Pavon 76) and two oetoptoid tritieate lines (T8t, T82) were tested mainly for eatlus induction and polyhaploid production on eaeh of the 11 media. The cultivar X medium interaction was not significant. When averaged over all growth regulators, Pavon was the best cultivar which produeed 14.4 % ealli and 23 % polyhaploid plantlets. Averaged over alt cultivars, the medium containing 2,4-D produced the highest ealli (t3.9 %). Undifferentiated ealli were regenerated on S7T1 medium, which contained lAA (1 mg/1) and kinetin (2 mg/1).
Nitrogen (N) is a critical factor for crop growth and yield. Improving nitrogen use efficiency (NUE) in agricultural systems is crucial for sustainable food production. However, the underlying regulation of N uptake and utilization in crops is not well known. Here, we identified OsSNAC1 (stress-responsive NAC 1) as an upstream regulator of OsNRT2.1 (nitrate transporter 2.1) in rice (Oryza sativa) by yeast one-hybridization screening. OsSNAC1 was mainly expressed in roots and shoots and induced by N deficiency. We observed similar expression patterns of OsSNAC1, OsNRT2.1/2.2, and OsNRT1.1A/B in response to NO3- supply. Overexpression of OsSNAC1 resulted in increased concentrations of free NO3- in roots and shoots, as well as higher N uptake, higher NUE and nitrogen use index (NUI) in rice plants, which conferred increased plant biomass and grain yield. On the contrary, mutation of OsSNAC1 resulted in decreased N uptake and lower NUI, which inhibited plant growth and yield. OsSNAC1 overexpression significantly upregulated OsNRT2.1/2.2 and OsNRT1.1A/B expression, while the mutation of OsSNAC1 significantly downregulated OsNRT2.1/2.2 and OsNRT1.1A/B expression. Y1H, transient co-expression and ChIP assays showed OsSNAC1 directly binds to the upstream promoter region of OsNRT2.1/2.2 and OsNRT1.1A/1.1B. In conclusion, we identified a NAC transcription factor in rice, OsSNAC1, with a positive role in regulating NO3- uptake through directly binding to the upstream promoter region of OsNRT2.1/2.2 and OsNRT1.1A/1.1B and activating their expression. Our results provide a potential genetic approach for improving crop NUE in agriculture.
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