Stem-changing Spanish i>y verbs in the present subjunctive

In Spanish some verbs ending in -uir undergo a stem change in the present subjunctive, in a very similar way they do in the present indicative. They will switch the -i for -y. The difference is that while in the present indicative the nosotros and vosotros forms do not change, in the present subjunctive all forms are affected by this change.
Have a look at these tables showing both the present indicative and the present subjunctive of construir (to build):

	CONSTRUIR (present indicative)	CONSTRUIR (present subjunctive)
yo	construyo	construya
tú	construyes	construyas
él / ella / usted	construye	construya
nosotros / nosotras	construimos	construyamos
vosotros / vosotras	construís	construyáis
ellos / ellas/ ustedes	construyen	construyan