Abstract
The elongation and development of wheat (Triticum aestivum L.) stem play an important role in plant architecture. The shortened stem would result in a sheathed spike and a low yield in crops. Unraveling the molecular mechanisms underlying a sheathed spike would be beneficial for plant architecture and yield improvement. We identified 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 was significantly decreased and the spike was not completely elongated and enclosed in flag leaf sheaths. Moreover, the increase in 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 which was only half the length of the wild-type. The size of parenchyma cells was obviously reduced and cell length on the longitudinal section was elongated insufficiently compared with wild-type. The analysis of hormone content showed that there was a lack of gibberellin A 3 (GA3) in internodes but a higher brassinosteroid (BR) content. TaWUS-like may inhibit the synthesis of GA3 and/or BR, thus affecting the function of signal transduction of these hormones, which further caused stem shortening and plant dwarfing in wheat.
Highlights
Plant architecture is a key agronomical factor determining crop yield [1]
The TaWUS-like-OE lines showed sheathed spikes that were wrapped full- or half- by the flag leaf sheath (Figure 1A,B) at the heading stage. This phenotype could be found at the filling stage of wheat, even after harvest, the spike could not be completely elongated from the leaf sheath (Figure 1D)
We believe that the shortening of internodes of wheat is related to the obvious inhibition of cell division and longitudinal elongation by TaWUS-like, while gibberellic acid (GA) and BR together are involved in the regulation of genes expression of stem development, which is different from the previous reports that GA or BR alone regulates internode elongation [5,20,25]
Summary
Plant architecture is a key agronomical factor determining crop yield [1]. As an important food crop, with the rapid expansion of large population and the shrinking of cultivated land areas, the demand for wheat production will be greatly increased in the future. It is an urgent and essential task for wheat breeding to understand and improve wheat yield by the engineering of plant architecture [2,3]. The sheathed panicle was relieved by exogenous spraying GA in the leaves. The detailed molecular mechanisms of the sheathed panicle are still unclear
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