Enhancement of developmental defects in the boron‐deficient maize mutanttassel‐less1by reduced auxin levels

Abstract

AbstractBackgroundPlant responses to deficiencies of the micronutrient boron are diverse and go beyond the well‐characterized function of boron in cell wall crosslinking. To explain these phenotypic discrepancies, hypotheses about interactions of boron with various phytohormones have been proposed, particularly auxin. While these hypotheses are intensely tested in the root meristem of the model species,Arabidopsis thaliana, studies in crop species and the shoot are limited.AimsTo address potential boron–auxin interactions during the vegetative and reproductive development of the crop maize (Zea mays), we utilized the boron‐deficienttassel‐less1(tls1) mutant and the auxin‐deficientvanishing tassel2(vt2) mutant. We investigated interactions of boron and auxin on the levels of auxin biosynthesis and auxin transport in leaves and shoot meristems.Methods and ResultsBy using genetic interaction analysis, hormone quantification, and confocal microscopy, we show that boron‐deficient leaf phenotypes intls1are enhanced in double mutants withvt2in both greenhouse and field conditions. However, auxin levels are not altered in developing leaves intls1. Rather, the localization ofZmPIN1a:YFP, a marker for auxin transport, is altered in young tassel meristems and is absent from organ initiation sites during vegetative development.ConclusionsOur data suggest a link between polar auxin transport and phenotypic consequences in boron‐deficient conditions and further show that boron deficiency‐induced developmental defects are sensitive to low auxin levels. Our study, therefore, offers new insight into nutrient–hormone interactions to regulate crop development.